Migrate //chrome/browser/ui/webui/settings/ash to namespace ash [3/N]

This CL migrates os_settings_* files and included files (except
_sections*) to namespace ash.

This CL is part of the Chrome OS source code directory migration:
https://docs.google.com/document/d/1g-98HpzA8XcoGBWUv1gQNr4rbnD5yfvbtYZyPDDbkaE.

Bug: 1164001
Change-Id: I8d112840e02c4b2e8f39cec6ab8475a67635e3fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3937296
Owners-Override: Hidehiko Abe <[email protected]>
Reviewed-by: Hidehiko Abe <[email protected]>
Commit-Queue: Yeunjoo Choi <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1057415}
diff --git a/chrome/browser/ash/sync/os_sync_util_unittest.cc b/chrome/browser/ash/sync/os_sync_util_unittest.cc
index f10eee5..e32a4e4 100644
--- a/chrome/browser/ash/sync/os_sync_util_unittest.cc
+++ b/chrome/browser/ash/sync/os_sync_util_unittest.cc
@@ -19,7 +19,7 @@
  public:
   OsSyncUtilTest() {
     syncer::SyncPrefs::RegisterProfilePrefs(prefs_.registry());
-    chromeos::settings::OSSettingsUI::RegisterProfilePrefs(prefs_.registry());
+    ash::settings::OSSettingsUI::RegisterProfilePrefs(prefs_.registry());
   }
 
   sync_preferences::TestingPrefServiceSyncable prefs_;
diff --git a/chrome/browser/chrome_browser_interface_binders.cc b/chrome/browser/chrome_browser_interface_binders.cc
index 33f38bfb..6c04eed 100644
--- a/chrome/browser/chrome_browser_interface_binders.cc
+++ b/chrome/browser/chrome_browser_interface_binders.cc
@@ -1048,36 +1048,36 @@
       map);
 
   RegisterWebUIControllerInterfaceBinder<
-      app_management::mojom::PageHandlerFactory,
-      chromeos::settings::OSSettingsUI>(map);
+      app_management::mojom::PageHandlerFactory, ash::settings::OSSettingsUI>(
+      map);
 
   RegisterWebUIControllerInterfaceBinder<
-      ash::settings::mojom::UserActionRecorder,
-      chromeos::settings::OSSettingsUI>(map);
+      ash::settings::mojom::UserActionRecorder, ash::settings::OSSettingsUI>(
+      map);
 
   RegisterWebUIControllerInterfaceBinder<ash::settings::mojom::SearchHandler,
-                                         chromeos::settings::OSSettingsUI>(map);
+                                         ash::settings::OSSettingsUI>(map);
 
   RegisterWebUIControllerInterfaceBinder<
       ash::personalization_app::mojom::SearchHandler,
-      chromeos::settings::OSSettingsUI>(map);
+      ash::settings::OSSettingsUI>(map);
 
   RegisterWebUIControllerInterfaceBinder<
       ash::settings::app_notification::mojom::AppNotificationsHandler,
-      chromeos::settings::OSSettingsUI>(map);
+      ash::settings::OSSettingsUI>(map);
 
   RegisterWebUIControllerInterfaceBinder<
-      ash::cellular_setup::mojom::CellularSetup,
-      chromeos::settings::OSSettingsUI>(map);
+      ash::cellular_setup::mojom::CellularSetup, ash::settings::OSSettingsUI>(
+      map);
 
   RegisterWebUIControllerInterfaceBinder<ash::auth::mojom::AuthFactorConfig,
-                                         chromeos::settings::OSSettingsUI>(map);
+                                         ash::settings::OSSettingsUI>(map);
 
   RegisterWebUIControllerInterfaceBinder<ash::auth::mojom::RecoveryFactorEditor,
-                                         chromeos::settings::OSSettingsUI>(map);
+                                         ash::settings::OSSettingsUI>(map);
 
   RegisterWebUIControllerInterfaceBinder<
-      ash::cellular_setup::mojom::ESimManager, chromeos::settings::OSSettingsUI,
+      ash::cellular_setup::mojom::ESimManager, ash::settings::OSSettingsUI,
       chromeos::NetworkUI, chromeos::OobeUI>(map);
 
   RegisterWebUIControllerInterfaceBinder<
@@ -1111,7 +1111,7 @@
       ash::cfm::NetworkSettingsDialogUi,
 #endif  // BUILDFLAG(PLATFORM_CFM)
       chromeos::InternetConfigDialogUI, chromeos::InternetDetailDialogUI,
-      chromeos::NetworkUI, chromeos::OobeUI, chromeos::settings::OSSettingsUI,
+      chromeos::NetworkUI, chromeos::OobeUI, ash::settings::OSSettingsUI,
       chromeos::LockScreenNetworkUI, ash::ShimlessRMADialogUI>(map);
 
   RegisterWebUIControllerInterfaceBinder<
@@ -1235,13 +1235,12 @@
 
   RegisterWebUIControllerInterfaceBinder<
       ash::bluetooth_config::mojom::CrosBluetoothConfig,
-      chromeos::BluetoothPairingDialogUI, chromeos::settings::OSSettingsUI>(
-      map);
+      chromeos::BluetoothPairingDialogUI, ash::settings::OSSettingsUI>(map);
 
   if (ash::features::IsAudioSettingsPageEnabled()) {
     RegisterWebUIControllerInterfaceBinder<
-        ash::audio_config::mojom::CrosAudioConfig,
-        chromeos::settings::OSSettingsUI>(map);
+        ash::audio_config::mojom::CrosAudioConfig, ash::settings::OSSettingsUI>(
+        map);
   }
 
   RegisterWebUIControllerInterfaceBinder<audio::mojom::PageHandlerFactory,
@@ -1297,19 +1296,17 @@
   // Nearby Share receivers are bound.
   if (base::FeatureList::IsEnabled(features::kNearbySharing)) {
     RegisterWebUIControllerInterfaceBinder<
-        nearby_share::mojom::NearbyShareSettings,
-        chromeos::settings::OSSettingsUI, nearby_share::NearbyShareDialogUI>(
-        map);
+        nearby_share::mojom::NearbyShareSettings, ash::settings::OSSettingsUI,
+        nearby_share::NearbyShareDialogUI>(map);
     RegisterWebUIControllerInterfaceBinder<nearby_share::mojom::ContactManager,
-                                           chromeos::settings::OSSettingsUI,
+                                           ash::settings::OSSettingsUI,
                                            nearby_share::NearbyShareDialogUI>(
         map);
     RegisterWebUIControllerInterfaceBinder<
         nearby_share::mojom::DiscoveryManager,
         nearby_share::NearbyShareDialogUI>(map);
     RegisterWebUIControllerInterfaceBinder<nearby_share::mojom::ReceiveManager,
-                                           chromeos::settings::OSSettingsUI>(
-        map);
+                                           ash::settings::OSSettingsUI>(map);
   }
 #endif  // BUILDFLAG(IS_CHROMEOS_ASH)
 
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 207cac7..e8dacf7 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -1494,7 +1494,7 @@
   chromeos::EduCoexistenceLoginHandler::RegisterProfilePrefs(registry);
   ash::SigninErrorNotifier::RegisterPrefs(registry);
   ash::ServicesCustomizationDocument::RegisterProfilePrefs(registry);
-  chromeos::settings::OSSettingsUI::RegisterProfilePrefs(registry);
+  ash::settings::OSSettingsUI::RegisterProfilePrefs(registry);
   ash::StartupUtils::RegisterOobeProfilePrefs(registry);
   ash::UserImageSyncObserver::RegisterProfilePrefs(registry);
   ChromeMetricsServiceClient::RegisterProfilePrefs(registry);
diff --git a/chrome/browser/ui/app_list/search/os_settings_provider.cc b/chrome/browser/ui/app_list/search/os_settings_provider.cc
index 6ed5850..68829e3 100644
--- a/chrome/browser/ui/app_list/search/os_settings_provider.cc
+++ b/chrome/browser/ui/app_list/search/os_settings_provider.cc
@@ -63,7 +63,7 @@
 
 bool ContainsBetterAncestor(Subpage subpage,
                             const double score,
-                            const chromeos::settings::Hierarchy* hierarchy,
+                            const ash::settings::Hierarchy* hierarchy,
                             const base::flat_map<Subpage, double>& subpages,
                             const base::flat_map<Section, double>& sections) {
   // Returns whether or not a higher-scoring ancestor subpage or section of
@@ -86,7 +86,7 @@
 
 bool ContainsBetterAncestor(Setting setting,
                             const double score,
-                            const chromeos::settings::Hierarchy* hierarchy,
+                            const ash::settings::Hierarchy* hierarchy,
                             const base::flat_map<Subpage, double>& subpages,
                             const base::flat_map<Section, double>& sections) {
   // Returns whether or not a higher-scoring ancestor subpage or section of
@@ -165,8 +165,7 @@
 OsSettingsProvider::OsSettingsProvider(Profile* profile)
     : profile_(profile),
       settings_manager_(
-          chromeos::settings::OsSettingsManagerFactory::GetForProfile(
-              profile)) {
+          ash::settings::OsSettingsManagerFactory::GetForProfile(profile)) {
   DCHECK(profile_);
 
   if (settings_manager_) {
@@ -316,7 +315,7 @@
 std::vector<SettingsResultPtr> OsSettingsProvider::FilterResults(
     const std::u16string& query,
     const std::vector<SettingsResultPtr>& results,
-    const chromeos::settings::Hierarchy* hierarchy) {
+    const ash::settings::Hierarchy* hierarchy) {
   base::flat_set<std::string> seen_urls;
   base::flat_map<Subpage, double> seen_subpages;
   base::flat_map<Section, double> seen_sections;
diff --git a/chrome/browser/ui/app_list/search/os_settings_provider.h b/chrome/browser/ui/app_list/search/os_settings_provider.h
index 69adb856..3af297bc 100644
--- a/chrome/browser/ui/app_list/search/os_settings_provider.h
+++ b/chrome/browser/ui/app_list/search/os_settings_provider.h
@@ -21,15 +21,10 @@
 class Profile;
 
 namespace ash::settings {
-class SearchHandler;
-}
-
-namespace chromeos {
-namespace settings {
 class Hierarchy;
 class OsSettingsManager;
-}  // namespace settings
-}  // namespace chromeos
+class SearchHandler;
+}  // namespace ash::settings
 
 namespace gfx {
 class ImageSkia;
@@ -109,7 +104,7 @@
   std::vector<ash::settings::mojom::SearchResultPtr> FilterResults(
       const std::u16string& query,
       const std::vector<ash::settings::mojom::SearchResultPtr>& results,
-      const chromeos::settings::Hierarchy* hierarchy);
+      const ash::settings::Hierarchy* hierarchy);
 
   void OnLoadIcon(apps::IconValuePtr icon_value);
 
@@ -121,9 +116,9 @@
   float min_score_for_alternates_ = 0.4f;
 
   Profile* const profile_;
-  chromeos::settings::OsSettingsManager* const settings_manager_;
+  ash::settings::OsSettingsManager* const settings_manager_;
   ash::settings::SearchHandler* search_handler_;
-  const chromeos::settings::Hierarchy* hierarchy_;
+  const ash::settings::Hierarchy* hierarchy_;
   apps::AppServiceProxy* app_service_proxy_;
   gfx::ImageSkia icon_;
 
diff --git a/chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc b/chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc
index 4dbf23ed..a3ede9a 100644
--- a/chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc
+++ b/chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc
@@ -1036,7 +1036,7 @@
     return nullptr;
   }
   if (url.host_piece() == chrome::kChromeUIOSSettingsHost)
-    return &NewWebUI<chromeos::settings::OSSettingsUI>;
+    return &NewWebUI<ash::settings::OSSettingsUI>;
   if (url.host_piece() == chrome::kChromeUIPowerHost)
     return &NewWebUI<chromeos::PowerUI>;
   if (url.host_piece() == ash::kChromeUIDiagnosticsAppHost) {
diff --git a/chrome/browser/ui/webui/settings/ash/about_section.h b/chrome/browser/ui/webui/settings/ash/about_section.h
index c38f2e7..229c00a2 100644
--- a/chrome/browser/ui/webui/settings/ash/about_section.h
+++ b/chrome/browser/ui/webui/settings/ash/about_section.h
@@ -56,4 +56,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::AboutSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_ABOUT_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/accessibility_section.h b/chrome/browser/ui/webui/settings/ash/accessibility_section.h
index 14d656d..138ae006 100644
--- a/chrome/browser/ui/webui/settings/ash/accessibility_section.h
+++ b/chrome/browser/ui/webui/settings/ash/accessibility_section.h
@@ -66,4 +66,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::AccessibilitySection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_ACCESSIBILITY_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/apps_section.h b/chrome/browser/ui/webui/settings/ash/apps_section.h
index 37c2536..b62b34c 100644
--- a/chrome/browser/ui/webui/settings/ash/apps_section.h
+++ b/chrome/browser/ui/webui/settings/ash/apps_section.h
@@ -68,4 +68,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::AppsSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_APPS_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/bluetooth_section.h b/chrome/browser/ui/webui/settings/ash/bluetooth_section.h
index 283357a..b3644b8 100644
--- a/chrome/browser/ui/webui/settings/ash/bluetooth_section.h
+++ b/chrome/browser/ui/webui/settings/ash/bluetooth_section.h
@@ -72,4 +72,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::BluetoothSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_BLUETOOTH_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/crostini_section.h b/chrome/browser/ui/webui/settings/ash/crostini_section.h
index 67e6087..5898f7e3 100644
--- a/chrome/browser/ui/webui/settings/ash/crostini_section.h
+++ b/chrome/browser/ui/webui/settings/ash/crostini_section.h
@@ -54,4 +54,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::CrostiniSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_CROSTINI_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/date_time_section.h b/chrome/browser/ui/webui/settings/ash/date_time_section.h
index f6b537d4..93b3f410 100644
--- a/chrome/browser/ui/webui/settings/ash/date_time_section.h
+++ b/chrome/browser/ui/webui/settings/ash/date_time_section.h
@@ -38,4 +38,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::DateTimeSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_DATE_TIME_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/device_section.h b/chrome/browser/ui/webui/settings/ash/device_section.h
index 6c8da0b..491559d 100644
--- a/chrome/browser/ui/webui/settings/ash/device_section.h
+++ b/chrome/browser/ui/webui/settings/ash/device_section.h
@@ -97,4 +97,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::DeviceSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_DEVICE_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/fake_hierarchy.cc b/chrome/browser/ui/webui/settings/ash/fake_hierarchy.cc
index 8b8d84e..2325724 100644
--- a/chrome/browser/ui/webui/settings/ash/fake_hierarchy.cc
+++ b/chrome/browser/ui/webui/settings/ash/fake_hierarchy.cc
@@ -8,14 +8,12 @@
 
 #include "chrome/browser/ui/webui/settings/ash/fake_os_settings_section.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
-// TODO(https://crbug.com/1164001): remove after migrating to ash.
 namespace mojom {
-using ::ash::settings::mojom::SearchResultDefaultRank;
-using ::ash::settings::mojom::SearchResultIcon;
-using ::ash::settings::mojom::SearchResultType;
+using ::chromeos::settings::mojom::Section;
+using ::chromeos::settings::mojom::Setting;
+using ::chromeos::settings::mojom::Subpage;
 }  // namespace mojom
 
 FakeHierarchy::FakeHierarchy(const OsSettingsSections* sections)
@@ -56,5 +54,4 @@
   return FakeOsSettingsSection::ModifySearchResultUrl(section, url_to_modify);
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/fake_hierarchy.h b/chrome/browser/ui/webui/settings/ash/fake_hierarchy.h
index ddc5677..bdd7f49 100644
--- a/chrome/browser/ui/webui/settings/ash/fake_hierarchy.h
+++ b/chrome/browser/ui/webui/settings/ash/fake_hierarchy.h
@@ -8,8 +8,7 @@
 #include "chrome/browser/ui/webui/settings/ash/hierarchy.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 class OsSettingsSections;
 
@@ -22,34 +21,28 @@
   FakeHierarchy& operator=(const FakeHierarchy& other) = delete;
   ~FakeHierarchy() override;
 
-  void AddSubpageMetadata(
-      int name_message_id,
-      mojom::Section section,
-      mojom::Subpage subpage,
-      ash::settings::mojom::SearchResultIcon icon,
-      ash::settings::mojom::SearchResultDefaultRank default_rank,
-      const std::string& url_path_with_parameters,
-      absl::optional<mojom::Subpage> parent_subpage = absl::nullopt);
-  void AddSettingMetadata(
-      mojom::Section section,
-      mojom::Setting setting,
-      absl::optional<mojom::Subpage> parent_subpage = absl::nullopt);
+  void AddSubpageMetadata(int name_message_id,
+                          chromeos::settings::mojom::Section section,
+                          chromeos::settings::mojom::Subpage subpage,
+                          mojom::SearchResultIcon icon,
+                          mojom::SearchResultDefaultRank default_rank,
+                          const std::string& url_path_with_parameters,
+                          absl::optional<chromeos::settings::mojom::Subpage>
+                              parent_subpage = absl::nullopt);
+  void AddSettingMetadata(chromeos::settings::mojom::Section section,
+                          chromeos::settings::mojom::Setting setting,
+                          absl::optional<chromeos::settings::mojom::Subpage>
+                              parent_subpage = absl::nullopt);
 
  private:
   // Hierarchy:
   std::string ModifySearchResultUrl(
-      mojom::Section section,
-      ash::settings::mojom::SearchResultType type,
+      chromeos::settings::mojom::Section section,
+      mojom::SearchResultType type,
       OsSettingsIdentifier id,
       const std::string& url_to_modify) const override;
 };
 
-}  // namespace settings
-}  // namespace chromeos
-
-// TODO(https://crbug.com/1164001): remove when it moved to ash.
-namespace ash::settings {
-using ::chromeos::settings::FakeHierarchy;
-}
+}  // namespace ash::settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_FAKE_HIERARCHY_H_
diff --git a/chrome/browser/ui/webui/settings/ash/fake_os_settings_section.cc b/chrome/browser/ui/webui/settings/ash/fake_os_settings_section.cc
index 3b4b2aab..eee4e11 100644
--- a/chrome/browser/ui/webui/settings/ash/fake_os_settings_section.cc
+++ b/chrome/browser/ui/webui/settings/ash/fake_os_settings_section.cc
@@ -8,14 +8,11 @@
 
 #include "chrome/grit/generated_resources.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
-// TODO(https://crbug.com/1164001): remove after migrating to ash.
 namespace mojom {
-using ::ash::settings::mojom::SearchResultDefaultRank;
-using ::ash::settings::mojom::SearchResultIcon;
-using ::ash::settings::mojom::SearchResultType;
+using ::chromeos::settings::mojom::Section;
+using ::chromeos::settings::mojom::Setting;
 }  // namespace mojom
 
 FakeOsSettingsSection::FakeOsSettingsSection(mojom::Section section)
@@ -61,5 +58,4 @@
   return ss.str();
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/fake_os_settings_section.h b/chrome/browser/ui/webui/settings/ash/fake_os_settings_section.h
index 960100db..05afaf2 100644
--- a/chrome/browser/ui/webui/settings/ash/fake_os_settings_section.h
+++ b/chrome/browser/ui/webui/settings/ash/fake_os_settings_section.h
@@ -11,20 +11,20 @@
 #include "base/values.h"
 #include "chrome/browser/ui/webui/settings/ash/os_settings_section.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 // Fake OsSettingsSection implementation.
 class FakeOsSettingsSection : public OsSettingsSection {
  public:
-  explicit FakeOsSettingsSection(mojom::Section section);
+  explicit FakeOsSettingsSection(chromeos::settings::mojom::Section section);
   ~FakeOsSettingsSection() override;
 
   FakeOsSettingsSection(const FakeOsSettingsSection& other) = delete;
   FakeOsSettingsSection& operator=(const FakeOsSettingsSection& other) = delete;
 
-  mojom::Section section() { return section_; }
-  const std::vector<mojom::Setting>& logged_metrics() const {
+  chromeos::settings::mojom::Section section() { return section_; }
+  const std::vector<chromeos::settings::mojom::Setting>& logged_metrics()
+      const {
     return logged_metrics_;
   }
 
@@ -35,32 +35,33 @@
   // Returns the settings app name as a default value.
   int GetSectionNameMessageId() const override;
 
-  mojom::Section GetSection() const override;
+  chromeos::settings::mojom::Section GetSection() const override;
 
   // These functions return arbitrary dummy values.
-  ash::settings::mojom::SearchResultIcon GetSectionIcon() const override;
+  mojom::SearchResultIcon GetSectionIcon() const override;
   std::string GetSectionPath() const override;
-  bool LogMetric(mojom::Setting setting, base::Value& value) const override;
+  bool LogMetric(chromeos::settings::mojom::Setting setting,
+                 base::Value& value) const override;
 
   // Prepends the section name and "::" to the URL in |concept|. For example, if
   // the URL is "networkDetails" and the section is mojom::Section::kNetwork,
   // the returned URL is "Section::kNetwork::networkDetails".
   std::string ModifySearchResultUrl(
-      ash::settings::mojom::SearchResultType type,
+      mojom::SearchResultType type,
       OsSettingsIdentifier id,
       const std::string& url_to_modify) const override;
 
   // Static function used to implement the function above.
-  static std::string ModifySearchResultUrl(mojom::Section section,
-                                           const std::string& url_to_modify);
+  static std::string ModifySearchResultUrl(
+      chromeos::settings::mojom::Section section,
+      const std::string& url_to_modify);
 
  private:
-  const mojom::Section section_;
+  const chromeos::settings::mojom::Section section_;
   // Use mutable to modify this vector within the overridden const LogMetric.
-  mutable std::vector<mojom::Setting> logged_metrics_;
+  mutable std::vector<chromeos::settings::mojom::Setting> logged_metrics_;
 };
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_FAKE_OS_SETTINGS_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/fake_os_settings_sections.cc b/chrome/browser/ui/webui/settings/ash/fake_os_settings_sections.cc
index 80cf0160..e9c97581 100644
--- a/chrome/browser/ui/webui/settings/ash/fake_os_settings_sections.cc
+++ b/chrome/browser/ui/webui/settings/ash/fake_os_settings_sections.cc
@@ -7,8 +7,7 @@
 #include "chrome/browser/ui/webui/settings/ash/fake_os_settings_section.h"
 #include "chrome/browser/ui/webui/settings/chromeos/constants/constants_util.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 FakeOsSettingsSections::FakeOsSettingsSections() : OsSettingsSections() {
   for (const auto& section : constants::AllSections()) {
@@ -20,5 +19,4 @@
 
 FakeOsSettingsSections::~FakeOsSettingsSections() = default;
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/fake_os_settings_sections.h b/chrome/browser/ui/webui/settings/ash/fake_os_settings_sections.h
index 7313e8b..c525ed08 100644
--- a/chrome/browser/ui/webui/settings/ash/fake_os_settings_sections.h
+++ b/chrome/browser/ui/webui/settings/ash/fake_os_settings_sections.h
@@ -7,8 +7,7 @@
 
 #include "chrome/browser/ui/webui/settings/ash/os_settings_sections.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 // Collection of FakeOsSettingsSections.
 class FakeOsSettingsSections : public OsSettingsSections {
@@ -20,12 +19,6 @@
   ~FakeOsSettingsSections() override;
 };
 
-}  // namespace settings
-}  // namespace chromeos
-
-// TODO(https://crbug.com/1164001): remove when it moved to ash.
-namespace ash::settings {
-using ::chromeos::settings::FakeOsSettingsSections;
-}
+}  // namespace ash::settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_FAKE_OS_SETTINGS_SECTIONS_H_
diff --git a/chrome/browser/ui/webui/settings/ash/files_section.h b/chrome/browser/ui/webui/settings/ash/files_section.h
index 026a6213..2efaa118 100644
--- a/chrome/browser/ui/webui/settings/ash/files_section.h
+++ b/chrome/browser/ui/webui/settings/ash/files_section.h
@@ -38,4 +38,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::FilesSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_FILES_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/hierarchy.cc b/chrome/browser/ui/webui/settings/ash/hierarchy.cc
index 9b7cf6d..3116d12 100644
--- a/chrome/browser/ui/webui/settings/ash/hierarchy.cc
+++ b/chrome/browser/ui/webui/settings/ash/hierarchy.cc
@@ -13,17 +13,12 @@
 #include "chrome/grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
-// TODO(https://crbug.com/1164001): remove after migrating to ash.
 namespace mojom {
-using ::ash::settings::mojom::SearchResult;
-using ::ash::settings::mojom::SearchResultDefaultRank;
-using ::ash::settings::mojom::SearchResultIcon;
-using ::ash::settings::mojom::SearchResultIdentifier;
-using ::ash::settings::mojom::SearchResultPtr;
-using ::ash::settings::mojom::SearchResultType;
+using ::chromeos::settings::mojom::Section;
+using ::chromeos::settings::mojom::Setting;
+using ::chromeos::settings::mojom::Subpage;
 }  // namespace mojom
 
 namespace {
@@ -324,5 +319,4 @@
   return hierarchy_strings;
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/hierarchy.h b/chrome/browser/ui/webui/settings/ash/hierarchy.h
index c8e2e78..86d722e 100644
--- a/chrome/browser/ui/webui/settings/ash/hierarchy.h
+++ b/chrome/browser/ui/webui/settings/ash/hierarchy.h
@@ -16,8 +16,7 @@
 #include "chrome/browser/ui/webui/settings/chromeos/constants/setting.mojom.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 class OsSettingsSections;
 
@@ -45,7 +44,8 @@
 
   class SectionMetadata {
    public:
-    SectionMetadata(mojom::Section section, const Hierarchy* hierarchy);
+    SectionMetadata(chromeos::settings::mojom::Section section,
+                    const Hierarchy* hierarchy);
     ~SectionMetadata();
 
     // Whether the only contents of the section is a link to a subpage.
@@ -55,50 +55,48 @@
     // tag as the search result text. |relevance_score| must be passed by the
     // client, since this result is being created manually instead of via query
     // matching.
-    ash::settings::mojom::SearchResultPtr ToSearchResult(
-        double relevance_score) const;
+    mojom::SearchResultPtr ToSearchResult(double relevance_score) const;
 
    private:
-    mojom::Section section_;
+    chromeos::settings::mojom::Section section_;
     const Hierarchy* hierarchy_;
   };
 
   class SubpageMetadata {
    public:
     SubpageMetadata(int name_message_id,
-                    mojom::Section section,
-                    mojom::Subpage subpage,
-                    ash::settings::mojom::SearchResultIcon icon,
-                    ash::settings::mojom::SearchResultDefaultRank default_rank,
+                    chromeos::settings::mojom::Section section,
+                    chromeos::settings::mojom::Subpage subpage,
+                    mojom::SearchResultIcon icon,
+                    mojom::SearchResultDefaultRank default_rank,
                     const std::string& url_path_with_parameters,
                     const Hierarchy* hierarchy);
     ~SubpageMetadata();
 
     // The section in which the subpage appears.
-    mojom::Section section;
+    chromeos::settings::mojom::Section section;
 
     // The parent subpage, if applicable. Only applies to nested subpages.
-    absl::optional<mojom::Subpage> parent_subpage;
+    absl::optional<chromeos::settings::mojom::Subpage> parent_subpage;
 
     // Generates a search result for this subpage, using the canonical search
     // tag as the search result text. |relevance_score| must be passed by the
     // client, since this result is being created manually instead of via query
     // matching.
-    ash::settings::mojom::SearchResultPtr ToSearchResult(
-        double relevance_score) const;
+    mojom::SearchResultPtr ToSearchResult(double relevance_score) const;
 
    private:
-    mojom::Subpage subpage_;
+    chromeos::settings::mojom::Subpage subpage_;
 
     // Message ID corresponding to the localized string used to describe this
     // subpage.
     int name_message_id_;
 
     // Icon used for this subpage.
-    ash::settings::mojom::SearchResultIcon icon_;
+    mojom::SearchResultIcon icon_;
 
     // Default rank; used to order returned results.
-    ash::settings::mojom::SearchResultDefaultRank default_rank_;
+    mojom::SearchResultDefaultRank default_rank_;
 
     // Static URL path, which may need to be modified via
     // |modify_url_callback_|.
@@ -111,10 +109,12 @@
   // its subpage. Some settings are embedded directly into the section and have
   // no associated subpage.
   using SettingLocation =
-      std::pair<mojom::Section, absl::optional<mojom::Subpage>>;
+      std::pair<chromeos::settings::mojom::Section,
+                absl::optional<chromeos::settings::mojom::Subpage>>;
 
   struct SettingMetadata {
-    explicit SettingMetadata(mojom::Section primary_section);
+    explicit SettingMetadata(
+        chromeos::settings::mojom::Section primary_section);
     ~SettingMetadata();
 
     // The primary location, as described above.
@@ -125,9 +125,12 @@
     std::vector<SettingLocation> alternates;
   };
 
-  const SectionMetadata& GetSectionMetadata(mojom::Section section) const;
-  const SubpageMetadata& GetSubpageMetadata(mojom::Subpage subpage) const;
-  const SettingMetadata& GetSettingMetadata(mojom::Setting setting) const;
+  const SectionMetadata& GetSectionMetadata(
+      chromeos::settings::mojom::Section section) const;
+  const SubpageMetadata& GetSubpageMetadata(
+      chromeos::settings::mojom::Subpage subpage) const;
+  const SettingMetadata& GetSettingMetadata(
+      chromeos::settings::mojom::Setting setting) const;
 
   // Generates a list of names of the ancestor sections/subpages for |subpage|.
   // The list contains the Settings app name, the section name and, if
@@ -140,39 +143,36 @@
   // Example 2 - External storage (has parent subpage):
   //                 ["Settings", "Device", "Storage management"]
   std::vector<std::u16string> GenerateAncestorHierarchyStrings(
-      mojom::Subpage subpage) const;
+      chromeos::settings::mojom::Subpage subpage) const;
 
   // Same as above, but for settings.
   std::vector<std::u16string> GenerateAncestorHierarchyStrings(
-      mojom::Setting setting) const;
+      chromeos::settings::mojom::Setting setting) const;
 
  protected:
-  std::unordered_map<mojom::Section, SectionMetadata> section_map_;
-  std::unordered_map<mojom::Subpage, SubpageMetadata> subpage_map_;
-  std::unordered_map<mojom::Setting, SettingMetadata> setting_map_;
+  std::unordered_map<chromeos::settings::mojom::Section, SectionMetadata>
+      section_map_;
+  std::unordered_map<chromeos::settings::mojom::Subpage, SubpageMetadata>
+      subpage_map_;
+  std::unordered_map<chromeos::settings::mojom::Setting, SettingMetadata>
+      setting_map_;
 
  private:
   class PerSectionHierarchyGenerator;
 
   // Generates an array with the Settings app name and |section|'s name.
   std::vector<std::u16string> GenerateHierarchyStrings(
-      mojom::Section section) const;
+      chromeos::settings::mojom::Section section) const;
 
   virtual std::string ModifySearchResultUrl(
-      mojom::Section section,
-      ash::settings::mojom::SearchResultType type,
+      chromeos::settings::mojom::Section section,
+      mojom::SearchResultType type,
       OsSettingsIdentifier id,
       const std::string& url_to_modify) const;
 
   const OsSettingsSections* sections_;
 };
 
-}  // namespace settings
-}  // namespace chromeos
-
-// TODO(https://crbug.com/1164001): remove when it moved to ash.
-namespace ash::settings {
-using ::chromeos::settings::Hierarchy;
-}
+}  // namespace ash::settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_HIERARCHY_H_
diff --git a/chrome/browser/ui/webui/settings/ash/internet_section.h b/chrome/browser/ui/webui/settings/ash/internet_section.h
index c8c9214d..89d7ec4 100644
--- a/chrome/browser/ui/webui/settings/ash/internet_section.h
+++ b/chrome/browser/ui/webui/settings/ash/internet_section.h
@@ -86,4 +86,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::InternetSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_INTERNET_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/kerberos_section.h b/chrome/browser/ui/webui/settings/ash/kerberos_section.h
index d3e33ad..2379919 100644
--- a/chrome/browser/ui/webui/settings/ash/kerberos_section.h
+++ b/chrome/browser/ui/webui/settings/ash/kerberos_section.h
@@ -53,4 +53,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::KerberosSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_KERBEROS_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/languages_section.h b/chrome/browser/ui/webui/settings/ash/languages_section.h
index 60ddd7f6..3e4ec2b 100644
--- a/chrome/browser/ui/webui/settings/ash/languages_section.h
+++ b/chrome/browser/ui/webui/settings/ash/languages_section.h
@@ -50,4 +50,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::LanguagesSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_LANGUAGES_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/main_section.h b/chrome/browser/ui/webui/settings/ash/main_section.h
index d66bfd7..f85a3d1 100644
--- a/chrome/browser/ui/webui/settings/ash/main_section.h
+++ b/chrome/browser/ui/webui/settings/ash/main_section.h
@@ -44,4 +44,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::MainSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_MAIN_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/multidevice_section.h b/chrome/browser/ui/webui/settings/ash/multidevice_section.h
index 0a65403..0e1a497 100644
--- a/chrome/browser/ui/webui/settings/ash/multidevice_section.h
+++ b/chrome/browser/ui/webui/settings/ash/multidevice_section.h
@@ -102,4 +102,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::MultiDeviceSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_MULTIDEVICE_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_browser_test_mixin.cc b/chrome/browser/ui/webui/settings/ash/os_settings_browser_test_mixin.cc
index 44a8649..4906166 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_browser_test_mixin.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_browser_test_mixin.cc
@@ -10,10 +10,19 @@
 #include "chrome/browser/ui/webui/settings/ash/os_settings_ui.h"
 #include "chrome/test/base/web_ui_test_data_source.h"
 #include "chrome/test/data/grit/webui_generated_test_resources_map.h"
+#include "chrome/test/data/webui/settings/chromeos/test_api.test-mojom-test-utils.h"
+#include "chrome/test/data/webui/settings/chromeos/test_api.test-mojom.h"
 #include "content/public/browser/web_ui_data_source.h"
 #include "ui/base/resource/resource_bundle.h"
 
-namespace chromeos::settings {
+namespace ash::settings {
+
+namespace mojom {
+using ::chromeos::settings::mojom::LockScreenSettingsAsyncWaiter;
+using ::chromeos::settings::mojom::OSSettingsBrowserProcess;
+using ::chromeos::settings::mojom::OSSettingsDriver;
+using ::chromeos::settings::mojom::OSSettingsDriverAsyncWaiter;
+}  // namespace mojom
 
 OSSettingsBrowserTestMixin::BrowserProcessServer::BrowserProcessServer() =
     default;
@@ -134,4 +143,4 @@
       lock_screen_settings_remotes_.Get(id));
 }
 
-}  // namespace chromeos::settings
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_browser_test_mixin.h b/chrome/browser/ui/webui/settings/ash/os_settings_browser_test_mixin.h
index c29ce47..8acd89f 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_browser_test_mixin.h
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_browser_test_mixin.h
@@ -24,7 +24,7 @@
 
 }  // namespace content
 
-namespace chromeos::settings {
+namespace ash::settings {
 
 // A browser test mixin that opens the chromeos settings webui page and injects
 // the corresponding Javascript test api into it. The mixin wires up and
@@ -44,14 +44,16 @@
 
   // Returns the mojo remote that can be used in C++ browser tests to
   // manipulate the os settings UI.
-  mojom::OSSettingsDriverAsyncWaiter OSSettingsDriver();
+  chromeos::settings::mojom::OSSettingsDriverAsyncWaiter OSSettingsDriver();
 
   // mojom::OSSettingsDriver functions, with return type wrapped into an
   // AsyncWaiter.
-  mojom::LockScreenSettingsAsyncWaiter GoToLockScreenSettings();
+  chromeos::settings::mojom::LockScreenSettingsAsyncWaiter
+  GoToLockScreenSettings();
 
  private:
-  class BrowserProcessServer : public mojom::OSSettingsBrowserProcess {
+  class BrowserProcessServer
+      : public chromeos::settings::mojom::OSSettingsBrowserProcess {
    public:
     BrowserProcessServer();
     ~BrowserProcessServer() override;
@@ -60,17 +62,22 @@
     BrowserProcessServer& operator=(const BrowserProcessServer&) = delete;
 
     void RegisterOSSettingsDriver(
-        mojo::PendingRemote<mojom::OSSettingsDriver> os_settings,
+        mojo::PendingRemote<chromeos::settings::mojom::OSSettingsDriver>
+            os_settings,
         base::OnceCallback<void()>) override;
 
-    mojom::OSSettingsDriver* OSSettingsDriver();
+    chromeos::settings::mojom::OSSettingsDriver* OSSettingsDriver();
 
-    void Bind(content::RenderFrameHost* render_frame_host,
-              mojo::PendingReceiver<mojom::OSSettingsBrowserProcess> receiver);
+    void Bind(
+        content::RenderFrameHost* render_frame_host,
+        mojo::PendingReceiver<
+            chromeos::settings::mojom::OSSettingsBrowserProcess> receiver);
 
    private:
-    absl::optional<mojo::Remote<mojom::OSSettingsDriver>> os_settings_driver_;
-    mojo::ReceiverSet<mojom::OSSettingsBrowserProcess> receivers_;
+    absl::optional<mojo::Remote<chromeos::settings::mojom::OSSettingsDriver>>
+        os_settings_driver_;
+    mojo::ReceiverSet<chromeos::settings::mojom::OSSettingsBrowserProcess>
+        receivers_;
   };
 
   class TestBrowserClient : public ChromeContentBrowserClient {
@@ -114,9 +121,10 @@
   // cleaned up when the mixin object is destroyed. Since it will usually not
   // contain more than perhaps a single digit number of remotes, this shouldn't
   // be a problem. mojo::RemoteSet<mojom::LockScreenSettings>
-  mojo::RemoteSet<mojom::LockScreenSettings> lock_screen_settings_remotes_;
+  mojo::RemoteSet<chromeos::settings::mojom::LockScreenSettings>
+      lock_screen_settings_remotes_;
 };
 
-}  // namespace chromeos::settings
+}  // namespace ash::settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_OS_SETTINGS_BROWSER_TEST_MIXIN_H_
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_features_util.cc b/chrome/browser/ui/webui/settings/ash/os_settings_features_util.cc
index 2bb4f6c..aff0ec4 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_features_util.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_features_util.cc
@@ -12,9 +12,7 @@
 #include "chrome/browser/profiles/profile_manager.h"
 #include "components/user_manager/user_manager.h"
 
-namespace chromeos {
-namespace settings {
-namespace features {
+namespace ash::settings::features {
 
 bool IsGuestModeActive() {
   return user_manager::UserManager::Get()->IsLoggedInAsGuest() ||
@@ -39,6 +37,4 @@
          arc::IsArcPlayStoreEnabledForProfile(profile);
 }
 
-}  // namespace features
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings::features
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_features_util.h b/chrome/browser/ui/webui/settings/ash/os_settings_features_util.h
index 602a2fb..6fb52b4b 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_features_util.h
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_features_util.h
@@ -7,9 +7,7 @@
 
 class Profile;
 
-namespace chromeos {
-namespace settings {
-namespace features {
+namespace ash::settings::features {
 
 bool IsGuestModeActive();
 
@@ -21,14 +19,13 @@
 // shown for |profile|.
 bool ShouldShowExternalStorageSettings(const Profile* profile);
 
-}  // namespace features
-}  // namespace settings
-}  // namespace chromeos
-
-// TODO(https://crbug.com/1164001): remove when it moved to ash.
-namespace ash::settings::features {
-using ::chromeos::settings::features::IsGuestModeActive;
-using ::chromeos::settings::features::ShouldShowExternalStorageSettings;
 }  // namespace ash::settings::features
 
+// TODO(https://crbug.com/1164001): remove when the migration is finished.
+namespace chromeos::settings::features {
+using ::ash::settings::features::IsGuestModeActive;
+using ::ash::settings::features::ShouldShowExternalStorageSettings;
+using ::ash::settings::features::ShouldShowParentalControlSettings;
+}  // namespace chromeos::settings::features
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_OS_SETTINGS_FEATURES_UTIL_H_
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_identifier.h b/chrome/browser/ui/webui/settings/ash/os_settings_identifier.h
index 91d4ef3..a4bafffd 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_identifier.h
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_identifier.h
@@ -8,22 +8,20 @@
 #include "chrome/browser/ui/webui/settings/chromeos/constants/routes.mojom.h"
 #include "chrome/browser/ui/webui/settings/chromeos/constants/setting.mojom.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 // Uniquely identifies a settings item (section, subpage, or setting).
 union OsSettingsIdentifier {
-  mojom::Section section;
-  mojom::Subpage subpage;
-  mojom::Setting setting;
+  chromeos::settings::mojom::Section section;
+  chromeos::settings::mojom::Subpage subpage;
+  chromeos::settings::mojom::Setting setting;
 };
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
 
-// TODO(https://crbug.com/1164001): remove when it moved to ash.
-namespace ash::settings {
-using ::chromeos::settings::OsSettingsIdentifier;
+// TODO(https://crbug.com/1164001): remove when the migration is finished.
+namespace chromeos::settings {
+using ::ash::settings::OsSettingsIdentifier;
 }
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_OS_SETTINGS_IDENTIFIER_H_
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_lock_screen_authentication_browsertest.cc b/chrome/browser/ui/webui/settings/ash/os_settings_lock_screen_authentication_browsertest.cc
index ee1e35b..7f0f374e 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_lock_screen_authentication_browsertest.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_lock_screen_authentication_browsertest.cc
@@ -26,7 +26,7 @@
 
 }  // namespace
 
-namespace chromeos::settings {
+namespace ash::settings {
 
 // Test of the authentication dialog in the lock screen page in os-settings.
 class OSSettingsLockScreenAuthenticationTest
@@ -53,7 +53,7 @@
   }
 
  protected:
-  ash::CryptohomeMixin cryptohome_{&mixin_host_};
+  CryptohomeMixin cryptohome_{&mixin_host_};
   OSSettingsBrowserTestMixin os_settings_{&mixin_host_};
 
  private:
@@ -82,4 +82,4 @@
                          testing::Values(Params{.use_auth_session = false},
                                          Params{.use_auth_session = true}));
 
-}  // namespace chromeos::settings
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_manager.cc b/chrome/browser/ui/webui/settings/ash/os_settings_manager.cc
index 65cd486..c2028a2 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_manager.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_manager.cc
@@ -15,8 +15,7 @@
 #include "content/public/browser/web_ui_data_source.h"
 #include "ui/base/l10n/l10n_util.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 OsSettingsManager::OsSettingsManager(
     Profile* profile,
@@ -31,7 +30,7 @@
     android_sms::AndroidSmsService* android_sms_service,
     CupsPrintersManager* printers_manager,
     apps::AppServiceProxy* app_service_proxy,
-    ash::eche_app::EcheAppManager* eche_app_manager)
+    eche_app::EcheAppManager* eche_app_manager)
     : search_tag_registry_(
           std::make_unique<SearchTagRegistry>(local_search_service_proxy)),
       sections_(
@@ -84,5 +83,4 @@
   search_tag_registry_.reset();
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_manager.h b/chrome/browser/ui/webui/settings/ash/os_settings_manager.h
index 243502d..be7a1fc 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_manager.h
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_manager.h
@@ -9,25 +9,7 @@
 
 #include "ash/webui/eche_app_ui/eche_app_manager.h"
 #include "base/gtest_prod_util.h"
-// TODO(https://crbug.com/1164001): move to forward declaration.
-#include "ash/components/phonehub/phone_hub_manager.h"
-// TODO(https://crbug.com/1164001): move to forward declaration
-#include "ash/services/multidevice_setup/public/cpp/multidevice_setup_client.h"
 #include "chrome/browser/apps/app_service/app_service_proxy_forward.h"
-// TODO(https://crbug.com/1164001): move to forward declaration.
-#include "chrome/browser/ash/android_sms/android_sms_service.h"
-// TODO(https://crbug.com/1164001): forward declare when moved ash
-#include "chrome/browser/ash/kerberos/kerberos_credentials_manager.h"
-// TODO(https://crbug.com/1164001): forward declare when moved ash
-#include "chrome/browser/ash/printing/cups_printers_manager.h"
-// TODO(https://crbug.com/1164001): move to forward declaration
-#include "chrome/browser/ui/webui/settings/ash/os_apps_page/app_notification_handler.h"
-// TODO(https://crbug.com/1164001): move to forward declaration
-#include "chrome/browser/ui/webui/settings/ash/search/search_handler.h"
-// TODO(https://crbug.com/1164001): move to forward declaration
-#include "chrome/browser/ui/webui/settings/ash/search/search_tag_registry.h"
-// TODO(https://crbug.com/1164001): forward declare when moved ash
-#include "chromeos/ash/components/local_search_service/public/cpp/local_search_service_proxy.h"
 #include "components/keyed_service/core/keyed_service.h"
 
 class ArcAppListPrefs;
@@ -47,10 +29,34 @@
 class SyncService;
 }  // namespace syncer
 
-namespace chromeos::settings {
+namespace ash {
 
+class CupsPrintersManager;
+class KerberosCredentialsManager;
+
+namespace android_sms {
+class AndroidSmsService;
+}
+
+namespace local_search_service {
+class LocalSearchServiceProxy;
+}
+
+namespace multidevice_setup {
+class MultiDeviceSetupClient;
+}
+
+namespace phonehub {
+class PhoneHubManager;
+}
+
+namespace settings {
+
+class AppNotificationHandler;
 class Hierarchy;
 class OsSettingsSections;
+class SearchHandler;
+class SearchTagRegistry;
 class SettingsUserActionTracker;
 
 // Manager for the Chrome OS settings page. This class is implemented as a
@@ -94,7 +100,7 @@
       android_sms::AndroidSmsService* android_sms_service,
       CupsPrintersManager* printers_manager,
       apps::AppServiceProxy* app_service_proxy,
-      ash::eche_app::EcheAppManager* eche_app_manager);
+      eche_app::EcheAppManager* eche_app_manager);
   OsSettingsManager(const OsSettingsManager& other) = delete;
   OsSettingsManager& operator=(const OsSettingsManager& other) = delete;
   ~OsSettingsManager() override;
@@ -134,6 +140,7 @@
   std::unique_ptr<AppNotificationHandler> app_notification_handler_;
 };
 
-}  // namespace chromeos::settings
+}  // namespace settings
+}  // namespace ash
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_OS_SETTINGS_MANAGER_H_
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_manager_factory.cc b/chrome/browser/ui/webui/settings/ash/os_settings_manager_factory.cc
index 5d3f485..c9945a6 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_manager_factory.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_manager_factory.cc
@@ -20,10 +20,7 @@
 #include "chrome/browser/ui/webui/settings/ash/os_settings_manager.h"
 #include "chromeos/ash/components/local_search_service/public/cpp/local_search_service_proxy_factory.h"
 
-namespace chromeos {
-namespace settings {
-
-namespace local_search_service = ::ash::local_search_service;
+namespace ash::settings {
 
 // static
 OsSettingsManager* OsSettingsManagerFactory::GetForProfile(Profile* profile) {
@@ -83,5 +80,4 @@
   return true;
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_manager_factory.h b/chrome/browser/ui/webui/settings/ash/os_settings_manager_factory.h
index cb0b1d9..15279a0 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_manager_factory.h
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_manager_factory.h
@@ -10,8 +10,7 @@
 
 class Profile;
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 class OsSettingsManager;
 
@@ -35,7 +34,6 @@
   bool ServiceIsNULLWhileTesting() const override;
 };
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_OS_SETTINGS_MANAGER_FACTORY_H_
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_manager_unittest.cc b/chrome/browser/ui/webui/settings/ash/os_settings_manager_unittest.cc
index 139257b..5a34afd 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_manager_unittest.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_manager_unittest.cc
@@ -33,10 +33,12 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/accessibility/accessibility_features.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
-namespace local_search_service = ::ash::local_search_service;
+namespace mojom {
+using ::chromeos::settings::mojom::Section;
+using ::chromeos::settings::mojom::Subpage;
+}  // namespace mojom
 
 // Verifies the OsSettingsManager initialization flow. Behavioral functionality
 // is tested via unit tests on the sub-elements owned by OsSettingsManager.
@@ -141,5 +143,4 @@
   }
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_recovery_browsertest.cc b/chrome/browser/ui/webui/settings/ash/os_settings_recovery_browsertest.cc
index c08501c..f516355a2 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_recovery_browsertest.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_recovery_browsertest.cc
@@ -26,7 +26,7 @@
 
 }  // namespace
 
-namespace chromeos::settings {
+namespace ash::settings {
 
 class OSSettingsRecoveryTestWithoutFeature
     : public MixinBasedInProcessBrowserTest {
@@ -73,10 +73,10 @@
 // TODO(b/239416325): This should eventually check state in fake user data
 // auth, not in the auth factor config mojo service.
 IN_PROC_BROWSER_TEST_F(OSSettingsRecoveryTestWithFeature, CheckingEnables) {
-  auto auth_factor_config = ash::auth::GetAuthFactorConfigForTesting();
-  auto recovery_editor = ash::auth::GetRecoveryFactorEditorForTesting();
+  auto auth_factor_config = auth::GetAuthFactorConfigForTesting();
+  auto recovery_editor = auth::GetRecoveryFactorEditorForTesting();
 
-  ASSERT_EQ(ash::auth::mojom::RecoveryFactorEditor::ConfigureResult::kSuccess,
+  ASSERT_EQ(auth::mojom::RecoveryFactorEditor::ConfigureResult::kSuccess,
             recovery_editor.Configure(kAuthToken, false));
 
   auto lock_screen_settings = os_settings_.GoToLockScreenSettings();
@@ -85,16 +85,16 @@
   lock_screen_settings.ToggleRecoveryConfiguration();
 
   EXPECT_TRUE(auth_factor_config.IsConfigured(
-      kAuthToken, ash::auth::mojom::AuthFactor::kRecovery));
+      kAuthToken, auth::mojom::AuthFactor::kRecovery));
 }
 
 // TODO(b/239416325): This should eventually check state in fake user data
 // auth, not in the auth factor config mojo service.
 IN_PROC_BROWSER_TEST_F(OSSettingsRecoveryTestWithFeature, UncheckingDisables) {
-  auto auth_factor_config = ash::auth::GetAuthFactorConfigForTesting();
-  auto recovery_editor = ash::auth::GetRecoveryFactorEditorForTesting();
+  auto auth_factor_config = auth::GetAuthFactorConfigForTesting();
+  auto recovery_editor = auth::GetRecoveryFactorEditorForTesting();
 
-  ASSERT_EQ(ash::auth::mojom::RecoveryFactorEditor::ConfigureResult::kSuccess,
+  ASSERT_EQ(auth::mojom::RecoveryFactorEditor::ConfigureResult::kSuccess,
             recovery_editor.Configure(kAuthToken, true));
 
   auto lock_screen_settings = os_settings_.GoToLockScreenSettings();
@@ -103,7 +103,7 @@
   lock_screen_settings.ToggleRecoveryConfiguration();
 
   EXPECT_FALSE(auth_factor_config.IsConfigured(
-      kAuthToken, ash::auth::mojom::AuthFactor::kRecovery));
+      kAuthToken, auth::mojom::AuthFactor::kRecovery));
 }
 
-}  // namespace chromeos::settings
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_section.cc b/chrome/browser/ui/webui/settings/ash/os_settings_section.cc
index e53c90cf..bd230e1c 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_section.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_section.cc
@@ -12,16 +12,12 @@
 #include "chrome/grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
-// TODO(https://crbug.com/1164001): remove after migrating to ash.
 namespace mojom {
-using ::ash::settings::mojom::SearchResult;
-using ::ash::settings::mojom::SearchResultDefaultRank;
-using ::ash::settings::mojom::SearchResultIdentifier;
-using ::ash::settings::mojom::SearchResultPtr;
-using ::ash::settings::mojom::SearchResultType;
+using ::chromeos::settings::mojom::Section;
+using ::chromeos::settings::mojom::Setting;
+using ::chromeos::settings::mojom::Subpage;
 }  // namespace mojom
 
 // static
@@ -101,5 +97,4 @@
   return ss.str();
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_section.h b/chrome/browser/ui/webui/settings/ash/os_settings_section.h
index 0437eca..91c3397 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_section.h
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_section.h
@@ -18,17 +18,14 @@
 
 class Profile;
 
-namespace ash::settings {
-class SearchTagRegistry;
-}
-
 namespace content {
 class WebUI;
 class WebUIDataSource;
 }  // namespace content
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
+
+class SearchTagRegistry;
 
 // Represents one top-level section of the settings app (i.e., one item on the
 // settings UI navigation).
@@ -62,38 +59,42 @@
     // Registers a subpage whose parent is this section.
     virtual void RegisterTopLevelSubpage(
         int name_message_id,
-        mojom::Subpage subpage,
-        ash::settings::mojom::SearchResultIcon icon,
-        ash::settings::mojom::SearchResultDefaultRank default_rank,
+        chromeos::settings::mojom::Subpage subpage,
+        mojom::SearchResultIcon icon,
+        mojom::SearchResultDefaultRank default_rank,
         const std::string& url_path_with_parameters) = 0;
 
     // Registers a subpage whose parent is another subpage in this section.
     virtual void RegisterNestedSubpage(
         int name_message_id,
-        mojom::Subpage subpage,
-        mojom::Subpage parent_subpage,
-        ash::settings::mojom::SearchResultIcon icon,
-        ash::settings::mojom::SearchResultDefaultRank default_rank,
+        chromeos::settings::mojom::Subpage subpage,
+        chromeos::settings::mojom::Subpage parent_subpage,
+        mojom::SearchResultIcon icon,
+        mojom::SearchResultDefaultRank default_rank,
         const std::string& url_path_with_parameters) = 0;
 
     // Registers a setting embedded directly in the section (i.e., not within a
     // subpage). This functions is for primary locations (see above).
-    virtual void RegisterTopLevelSetting(mojom::Setting setting) = 0;
+    virtual void RegisterTopLevelSetting(
+        chromeos::settings::mojom::Setting setting) = 0;
 
     // Registers a setting embedded within a subpage in this section. This
     // function is for primary locations (see above).
-    virtual void RegisterNestedSetting(mojom::Setting setting,
-                                       mojom::Subpage subpage) = 0;
+    virtual void RegisterNestedSetting(
+        chromeos::settings::mojom::Setting setting,
+        chromeos::settings::mojom::Subpage subpage) = 0;
 
     // Register an alternate location for a setting embedded directly in the
     // section (i.e., not within a subpage). This function is for alternate
     // locations (see above).
-    virtual void RegisterTopLevelAltSetting(mojom::Setting setting) = 0;
+    virtual void RegisterTopLevelAltSetting(
+        chromeos::settings::mojom::Setting setting) = 0;
 
     // Registers a setting embedded within a subpage in this section. This
     // function is for alternate locations (see above).
-    virtual void RegisterNestedAltSetting(mojom::Setting setting,
-                                          mojom::Subpage subpage) = 0;
+    virtual void RegisterNestedAltSetting(
+        chromeos::settings::mojom::Setting setting,
+        chromeos::settings::mojom::Subpage subpage) = 0;
   };
 
   virtual ~OsSettingsSection();
@@ -113,17 +114,18 @@
   virtual int GetSectionNameMessageId() const = 0;
 
   // Provides the Section enum for this section.
-  virtual mojom::Section GetSection() const = 0;
+  virtual chromeos::settings::mojom::Section GetSection() const = 0;
 
   // Provides the icon for this section.
-  virtual ash::settings::mojom::SearchResultIcon GetSectionIcon() const = 0;
+  virtual mojom::SearchResultIcon GetSectionIcon() const = 0;
 
   // Provides the path for this section.
   virtual std::string GetSectionPath() const = 0;
 
   // Logs metrics for the updated |setting| with optional |value|. Returns
   // whether the setting change was logged.
-  virtual bool LogMetric(mojom::Setting setting, base::Value& value) const = 0;
+  virtual bool LogMetric(chromeos::settings::mojom::Setting setting,
+                         base::Value& value) const = 0;
 
   // Registers the subpages and/or settings which reside in this section. Every
   // subpage and setting within a section must be registered, regardless of
@@ -136,33 +138,32 @@
   // function simply returns |url_to_modify|, which provides  functionality for
   // static URLs.
   virtual std::string ModifySearchResultUrl(
-      ash::settings::mojom::SearchResultType type,
+      mojom::SearchResultType type,
       OsSettingsIdentifier id,
       const std::string& url_to_modify) const;
 
   // Generates a search result corresponding to this section. |relevance_score|
   // must be passed by the client, since this result is being created manually
   // instead of via query matching.
-  ash::settings::mojom::SearchResultPtr GenerateSectionSearchResult(
+  mojom::SearchResultPtr GenerateSectionSearchResult(
       double relevance_score) const;
 
   static std::u16string GetHelpUrlWithBoard(const std::string& original_url);
 
  protected:
   static void RegisterNestedSettingBulk(
-      mojom::Subpage,
-      const base::span<const mojom::Setting>& settings,
+      chromeos::settings::mojom::Subpage,
+      const base::span<const chromeos::settings::mojom::Setting>& settings,
       HierarchyGenerator* generator);
 
-  OsSettingsSection(Profile* profile,
-                    ash::settings::SearchTagRegistry* search_tag_registry);
+  OsSettingsSection(Profile* profile, SearchTagRegistry* search_tag_registry);
 
   // Used by tests.
   OsSettingsSection();
 
   Profile* profile() { return profile_; }
   const Profile* profile() const { return profile_; }
-  ash::settings::SearchTagRegistry* registry() { return search_tag_registry_; }
+  SearchTagRegistry* registry() { return search_tag_registry_; }
 
  private:
   FRIEND_TEST_ALL_PREFIXES(OsSettingsSectionTest, Section);
@@ -174,21 +175,19 @@
 
   // If type is Setting, adds the kSettingIdUrlParam to the query parameter
   // and returns the deep linked url. Doesn't modify url otherwise.
-  static std::string GetDefaultModifiedUrl(
-      ash::settings::mojom::SearchResultType type,
-      OsSettingsIdentifier id,
-      const std::string& url_to_modify);
+  static std::string GetDefaultModifiedUrl(mojom::SearchResultType type,
+                                           OsSettingsIdentifier id,
+                                           const std::string& url_to_modify);
 
   Profile* profile_;
-  ash::settings::SearchTagRegistry* search_tag_registry_;
+  SearchTagRegistry* search_tag_registry_;
 };
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
 
-// TODO(https://crbug.com/1164001): remove when it moved to ash.
-namespace ash::settings {
-using ::chromeos::settings::OsSettingsSection;
+// TODO(https://crbug.com/1164001): remove when the migration is finished.
+namespace chromeos::settings {
+using ::ash::settings::OsSettingsSection;
 }
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_OS_SETTINGS_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_section_unittest.cc b/chrome/browser/ui/webui/settings/ash/os_settings_section_unittest.cc
index 546395a..7e07852 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_section_unittest.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_section_unittest.cc
@@ -7,14 +7,12 @@
 #include "chrome/browser/ui/webui/settings/chromeos/constants/setting.mojom.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
-// TODO(https://crbug.com/1164001): remove after migrating to ash.
 namespace mojom {
-using ::ash::settings::mojom::SearchResultDefaultRank;
-using ::ash::settings::mojom::SearchResultIcon;
-using ::ash::settings::mojom::SearchResultType;
+using ::chromeos::settings::mojom::Section;
+using ::chromeos::settings::mojom::Setting;
+using ::chromeos::settings::mojom::Subpage;
 }  // namespace mojom
 
 TEST(OsSettingsSectionTest, Section) {
@@ -52,5 +50,4 @@
                 /*url_to_modify=*/"networks?type=WiFi"));
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_sections.cc b/chrome/browser/ui/webui/settings/ash/os_settings_sections.cc
index a997bfc..73475bb 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_sections.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_sections.cc
@@ -27,8 +27,11 @@
 #include "chrome/browser/ui/webui/settings/ash/reset_section.h"
 #include "chrome/browser/ui/webui/settings/ash/search_section.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
+
+namespace mojom {
+using ::chromeos::settings::mojom::Section;
+}
 
 OsSettingsSections::OsSettingsSections(
     Profile* profile,
@@ -43,7 +46,7 @@
     android_sms::AndroidSmsService* android_sms_service,
     CupsPrintersManager* printers_manager,
     apps::AppServiceProxy* app_service_proxy,
-    ash::eche_app::EcheAppManager* eche_app_manager) {
+    eche_app::EcheAppManager* eche_app_manager) {
   // Special case: Main section does not have an associated enum value.
   sections_.push_back(
       std::make_unique<MainSection>(profile, search_tag_registry));
@@ -159,5 +162,4 @@
   return it->second;
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_sections.h b/chrome/browser/ui/webui/settings/ash/os_settings_sections.h
index 7a403f1..c2cca4c4 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_sections.h
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_sections.h
@@ -8,18 +8,8 @@
 #include <unordered_map>
 #include <vector>
 
-// TODO(https://crbug.com/1164001): move to forward declaration.
-#include "ash/components/phonehub/phone_hub_manager.h"
-// TODO(https://crbug.com/1164001): move to forward declaration
-#include "ash/services/multidevice_setup/public/cpp/multidevice_setup_client.h"
 #include "ash/webui/eche_app_ui/eche_app_manager.h"
 #include "chrome/browser/apps/app_service/app_service_proxy_forward.h"
-// TODO(https://crbug.com/1164001): move to forward declaration.
-#include "chrome/browser/ash/android_sms/android_sms_service.h"
-// TODO(https://crbug.com/1164001): forward declare when moved ash
-#include "chrome/browser/ash/kerberos/kerberos_credentials_manager.h"
-// TODO(https://crbug.com/1164001): forward declare when moved ash
-#include "chrome/browser/ash/printing/cups_printers_manager.h"
 #include "chrome/browser/ui/webui/settings/ash/os_settings_section.h"
 #include "chrome/browser/ui/webui/settings/chromeos/constants/routes.mojom.h"
 
@@ -35,7 +25,23 @@
 class SyncService;
 }  // namespace syncer
 
-namespace chromeos {
+namespace ash {
+
+class CupsPrintersManager;
+class KerberosCredentialsManager;
+
+namespace android_sms {
+class AndroidSmsService;
+}
+
+namespace multidevice_setup {
+class MultiDeviceSetupClient;
+}
+
+namespace phonehub {
+class PhoneHubManager;
+}
+
 namespace settings {
 
 // Collection of all OsSettingsSection implementations.
@@ -43,7 +49,7 @@
  public:
   OsSettingsSections(
       Profile* profile,
-      ash::settings::SearchTagRegistry* search_tag_registry,
+      SearchTagRegistry* search_tag_registry,
       multidevice_setup::MultiDeviceSetupClient* multidevice_setup_client,
       phonehub::PhoneHubManager* phone_hub_manager,
       syncer::SyncService* sync_service,
@@ -54,12 +60,13 @@
       android_sms::AndroidSmsService* android_sms_service,
       CupsPrintersManager* printers_manager,
       apps::AppServiceProxy* app_service_proxy,
-      ash::eche_app::EcheAppManager* eche_app_manager);
+      eche_app::EcheAppManager* eche_app_manager);
   OsSettingsSections(const OsSettingsSections& other) = delete;
   OsSettingsSections& operator=(const OsSettingsSections& other) = delete;
   virtual ~OsSettingsSections();
 
-  const OsSettingsSection* GetSection(mojom::Section section) const;
+  const OsSettingsSection* GetSection(
+      chromeos::settings::mojom::Section section) const;
 
   std::vector<std::unique_ptr<OsSettingsSection>>& sections() {
     return sections_;
@@ -69,16 +76,12 @@
   // Used by tests.
   OsSettingsSections();
 
-  std::unordered_map<mojom::Section, OsSettingsSection*> sections_map_;
+  std::unordered_map<chromeos::settings::mojom::Section, OsSettingsSection*>
+      sections_map_;
   std::vector<std::unique_ptr<OsSettingsSection>> sections_;
 };
 
 }  // namespace settings
-}  // namespace chromeos
-
-// TODO(https://crbug.com/1164001): remove when it moved to ash.
-namespace ash::settings {
-using ::chromeos::settings::OsSettingsSections;
-}
+}  // namespace ash
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_OS_SETTINGS_SECTIONS_H_
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_ui.cc b/chrome/browser/ui/webui/settings/ash/os_settings_ui.cc
index d786c62b..384ae229 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_ui.cc
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_ui.cc
@@ -59,14 +59,7 @@
 
 }  // namespace
 
-namespace chromeos {
-namespace settings {
-
-// TODO(https://crbug.com/1164001): remove after migrating to ash.
-namespace mojom {
-using ::ash::settings::mojom::SearchHandler;
-using ::ash::settings::mojom::UserActionRecorder;
-}  // namespace mojom
+namespace ash::settings {
 
 // static
 void OSSettingsUI::RegisterProfilePrefs(
@@ -115,19 +108,20 @@
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<ash::cellular_setup::mojom::CellularSetup> receiver) {
-  ash::cellular_setup::CellularSetupImpl::CreateAndBindToReciever(
+    mojo::PendingReceiver<cellular_setup::mojom::CellularSetup> receiver) {
+  cellular_setup::CellularSetupImpl::CreateAndBindToReciever(
       std::move(receiver));
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<ash::cellular_setup::mojom::ESimManager> receiver) {
-  ash::GetESimManager(std::move(receiver));
+    mojo::PendingReceiver<cellular_setup::mojom::ESimManager> receiver) {
+  GetESimManager(std::move(receiver));
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<network_config::mojom::CrosNetworkConfig> receiver) {
-  ash::GetNetworkConfigService(std::move(receiver));
+    mojo::PendingReceiver<chromeos::network_config::mojom::CrosNetworkConfig>
+        receiver) {
+  GetNetworkConfigService(std::move(receiver));
 }
 
 void OSSettingsUI::BindInterface(
@@ -145,23 +139,19 @@
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<::ash::personalization_app::mojom::SearchHandler>
-        receiver) {
+    mojo::PendingReceiver<personalization_app::mojom::SearchHandler> receiver) {
   auto* profile = Profile::FromWebUI(web_ui());
-  DCHECK(
-      ash::personalization_app::CanSeeWallpaperOrPersonalizationApp(profile));
+  DCHECK(personalization_app::CanSeeWallpaperOrPersonalizationApp(profile));
 
-  auto* search_handler =
-      ::ash::personalization_app::PersonalizationAppManagerFactory::
-          GetForBrowserContext(profile)
-              ->search_handler();
+  auto* search_handler = personalization_app::PersonalizationAppManagerFactory::
+                             GetForBrowserContext(profile)
+                                 ->search_handler();
   DCHECK(search_handler);
   search_handler->BindInterface(std::move(receiver));
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<
-        ash::settings::app_notification::mojom::AppNotificationsHandler>
+    mojo::PendingReceiver<app_notification::mojom::AppNotificationsHandler>
         receiver) {
   OsSettingsManagerFactory::GetForProfile(Profile::FromWebUI(web_ui()))
       ->app_notification_handler()
@@ -220,28 +210,27 @@
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<ash::bluetooth_config::mojom::CrosBluetoothConfig>
+    mojo::PendingReceiver<bluetooth_config::mojom::CrosBluetoothConfig>
         receiver) {
-  ash::GetBluetoothConfigService(std::move(receiver));
+  GetBluetoothConfigService(std::move(receiver));
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<ash::audio_config::mojom::CrosAudioConfig> receiver) {
+    mojo::PendingReceiver<audio_config::mojom::CrosAudioConfig> receiver) {
   DCHECK(features::IsAudioSettingsPageEnabled());
-  ash::GetAudioConfigService(std::move(receiver));
+  GetAudioConfigService(std::move(receiver));
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<ash::auth::mojom::AuthFactorConfig> receiver) {
-  ash::auth::BindToAuthFactorConfig(std::move(receiver));
+    mojo::PendingReceiver<auth::mojom::AuthFactorConfig> receiver) {
+  auth::BindToAuthFactorConfig(std::move(receiver));
 }
 
 void OSSettingsUI::BindInterface(
-    mojo::PendingReceiver<ash::auth::mojom::RecoveryFactorEditor> receiver) {
-  ash::auth::BindToRecoveryFactorEditor(std::move(receiver));
+    mojo::PendingReceiver<auth::mojom::RecoveryFactorEditor> receiver) {
+  auth::BindToRecoveryFactorEditor(std::move(receiver));
 }
 
 WEB_UI_CONTROLLER_TYPE_IMPL(OSSettingsUI)
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/os_settings_ui.h b/chrome/browser/ui/webui/settings/ash/os_settings_ui.h
index 23e427a1..1e97baf2 100644
--- a/chrome/browser/ui/webui/settings/ash/os_settings_ui.h
+++ b/chrome/browser/ui/webui/settings/ash/os_settings_ui.h
@@ -27,16 +27,15 @@
 #include "ui/webui/mojo_web_ui_controller.h"
 #include "ui/webui/resources/cr_components/app_management/app_management.mojom-forward.h"
 
-namespace ash::settings::mojom {
-class SearchHandler;
-}
-
 namespace user_prefs {
 class PrefRegistrySyncable;
 }  // namespace user_prefs
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
+
+namespace mojom {
+class SearchHandler;
+}
 
 // The WebUI handler for chrome://os-settings.
 class OSSettingsUI : public ui::MojoWebUIController {
@@ -53,46 +52,42 @@
   // Instantiates implementor of the mojom::CellularSetup mojo interface
   // passing the pending receiver that will be internally bound.
   void BindInterface(
-      mojo::PendingReceiver<ash::cellular_setup::mojom::CellularSetup>
-          receiver);
+      mojo::PendingReceiver<cellular_setup::mojom::CellularSetup> receiver);
 
   // Instantiates implementor of the mojom::ESimManager mojo interface
   // passing the pending receiver that will be internally bound.
   void BindInterface(
-      mojo::PendingReceiver<ash::cellular_setup::mojom::ESimManager> receiver);
+      mojo::PendingReceiver<cellular_setup::mojom::ESimManager> receiver);
 
   // Instantiates implementor of the mojom::CrosAudioConfig mojo interface
   // passing the pending receiver that will be internally bound.
   void BindInterface(
-      mojo::PendingReceiver<ash::audio_config::mojom::CrosAudioConfig>
-          receiver);
+      mojo::PendingReceiver<audio_config::mojom::CrosAudioConfig> receiver);
 
   // Instantiates implementor of the mojom::CrosNetworkConfig mojo interface
   // passing the pending receiver that will be internally bound.
   void BindInterface(
-      mojo::PendingReceiver<network_config::mojom::CrosNetworkConfig> receiver);
+      mojo::PendingReceiver<chromeos::network_config::mojom::CrosNetworkConfig>
+          receiver);
 
   // Instantiates implementor of the mojom::UserActionRecorder mojo interface
   // passing the pending receiver that will be internally bound.
-  void BindInterface(
-      mojo::PendingReceiver<ash::settings::mojom::UserActionRecorder> receiver);
+  void BindInterface(mojo::PendingReceiver<mojom::UserActionRecorder> receiver);
 
   // Instantiates implementor of the mojom::SearchHandler mojo interface
   // passing the pending receiver that will be internally bound.
-  void BindInterface(
-      mojo::PendingReceiver<ash::settings::mojom::SearchHandler> receiver);
+  void BindInterface(mojo::PendingReceiver<mojom::SearchHandler> receiver);
 
   // Instantiates implementor of the personalization app mojom::SearchHandler
   // mojo interface passing the pending receiver that will be internally bound.
   void BindInterface(
-      mojo::PendingReceiver<::ash::personalization_app::mojom::SearchHandler>
+      mojo::PendingReceiver<personalization_app::mojom::SearchHandler>
           receiver);
 
   // Instantiates implementor of the mojom::AppNotificationsHandler mojo
   // interface passing the pending receiver that will be internally bound.
   void BindInterface(
-      mojo::PendingReceiver<
-          ash::settings::app_notification::mojom::AppNotificationsHandler>
+      mojo::PendingReceiver<app_notification::mojom::AppNotificationsHandler>
           receiver);
 
   // Instantiates implementor of the mojom::PageHandlerFactory mojo interface
@@ -118,29 +113,27 @@
   // Instantiates implementor of the mojom::CrosBluetoothConfig mojo interface
   // passing the pending receiver that will be internally bound.
   void BindInterface(
-      mojo::PendingReceiver<ash::bluetooth_config::mojom::CrosBluetoothConfig>
+      mojo::PendingReceiver<bluetooth_config::mojom::CrosBluetoothConfig>
           receiver);
 
   // Binds to the cros authentication factor editing services.
   void BindInterface(
-      mojo::PendingReceiver<ash::auth::mojom::AuthFactorConfig> receiver);
+      mojo::PendingReceiver<auth::mojom::AuthFactorConfig> receiver);
   void BindInterface(
-      mojo::PendingReceiver<ash::auth::mojom::RecoveryFactorEditor> receiver);
+      mojo::PendingReceiver<auth::mojom::RecoveryFactorEditor> receiver);
 
  private:
   base::TimeTicks time_when_opened_;
 
   WebuiLoadTimer webui_load_timer_;
 
-  std::unique_ptr<ash::settings::mojom::UserActionRecorder>
-      user_action_recorder_;
+  std::unique_ptr<mojom::UserActionRecorder> user_action_recorder_;
   std::unique_ptr<AppManagementPageHandlerFactory>
       app_management_page_handler_factory_;
 
   WEB_UI_CONTROLLER_TYPE_DECL();
 };
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_OS_SETTINGS_UI_H_
diff --git a/chrome/browser/ui/webui/settings/ash/people_section.h b/chrome/browser/ui/webui/settings/ash/people_section.h
index 36b6682..44b00727 100644
--- a/chrome/browser/ui/webui/settings/ash/people_section.h
+++ b/chrome/browser/ui/webui/settings/ash/people_section.h
@@ -99,4 +99,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::PeopleSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_PEOPLE_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/personalization_section.h b/chrome/browser/ui/webui/settings/ash/personalization_section.h
index 540fa0a..cff0cd3 100644
--- a/chrome/browser/ui/webui/settings/ash/personalization_section.h
+++ b/chrome/browser/ui/webui/settings/ash/personalization_section.h
@@ -47,4 +47,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::PersonalizationSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_PERSONALIZATION_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/pref_names.h b/chrome/browser/ui/webui/settings/ash/pref_names.h
index 57cbbff..a9e7b5ab 100644
--- a/chrome/browser/ui/webui/settings/ash/pref_names.h
+++ b/chrome/browser/ui/webui/settings/ash/pref_names.h
@@ -15,4 +15,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings::prefs {
+using ::chromeos::settings::prefs::kSyncOsWallpaper;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_PREF_NAMES_H_
diff --git a/chrome/browser/ui/webui/settings/ash/printing_section.h b/chrome/browser/ui/webui/settings/ash/printing_section.h
index 5dccfce..3a391595 100644
--- a/chrome/browser/ui/webui/settings/ash/printing_section.h
+++ b/chrome/browser/ui/webui/settings/ash/printing_section.h
@@ -50,4 +50,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::PrintingSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_PRINTING_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/privacy_section.h b/chrome/browser/ui/webui/settings/ash/privacy_section.h
index 020bdec..62e8b3f 100644
--- a/chrome/browser/ui/webui/settings/ash/privacy_section.h
+++ b/chrome/browser/ui/webui/settings/ash/privacy_section.h
@@ -50,4 +50,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::PrivacySection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_PRIVACY_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/reset_section.h b/chrome/browser/ui/webui/settings/ash/reset_section.h
index dafeafb5..9c914d29 100644
--- a/chrome/browser/ui/webui/settings/ash/reset_section.h
+++ b/chrome/browser/ui/webui/settings/ash/reset_section.h
@@ -40,4 +40,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::ResetSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_RESET_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/search_section.h b/chrome/browser/ui/webui/settings/ash/search_section.h
index d376ac8..dd9aae6e 100644
--- a/chrome/browser/ui/webui/settings/ash/search_section.h
+++ b/chrome/browser/ui/webui/settings/ash/search_section.h
@@ -58,4 +58,9 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings {
+using ::chromeos::settings::SearchSection;
+}
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_SEARCH_SECTION_H_
diff --git a/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker.cc b/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker.cc
index f5d2e18..6cfa7f6 100644
--- a/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker.cc
+++ b/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker.cc
@@ -12,13 +12,7 @@
 #include "chrome/browser/ui/webui/settings/ash/hierarchy.h"
 #include "chrome/browser/ui/webui/settings/ash/os_settings_sections.h"
 
-namespace chromeos {
-namespace settings {
-
-// TODO(https://crbug.com/1164001): remove after migrating to ash.
-namespace mojom {
-using ::ash::settings::mojom::UserActionRecorder;
-}
+namespace ash::settings {
 
 SettingsUserActionTracker::SettingsUserActionTracker(
     Hierarchy* hierarchy,
@@ -77,12 +71,12 @@
 }
 
 void SettingsUserActionTracker::RecordSettingChangeWithDetails(
-    mojom::Setting setting,
-    ash::settings::mojom::SettingChangeValuePtr value) {
+    chromeos::settings::mojom::Setting setting,
+    mojom::SettingChangeValuePtr value) {
   per_session_tracker_->RecordSettingChange();
 
   // Get the primary section location of the changed setting and log the metric.
-  mojom::Section section_id =
+  chromeos::settings::mojom::Section section_id =
       hierarchy_->GetSettingMetadata(setting).primary.first;
   const OsSettingsSection* section = sections_->GetSection(section_id);
   // new_value is initialized as null. Null value is used in cases that don't
@@ -103,5 +97,4 @@
                            static_cast<int>(setting));
 }
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker.h b/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker.h
index 6fe2118..95b5bea 100644
--- a/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker.h
+++ b/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker.h
@@ -14,8 +14,7 @@
 #include "mojo/public/cpp/bindings/pending_receiver.h"
 #include "mojo/public/cpp/bindings/receiver.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
 class Hierarchy;
 class OsSettingsSections;
@@ -23,8 +22,7 @@
 // Records user actions within Settings. Utilizes a per session tracker that
 // measures the user's effort required to change a setting. Eventually uses
 // a per section tracker to record metrics in each section.
-class SettingsUserActionTracker
-    : public ash::settings::mojom::UserActionRecorder {
+class SettingsUserActionTracker : public mojom::UserActionRecorder {
  public:
   SettingsUserActionTracker(Hierarchy* hierarchy, OsSettingsSections* sections);
   SettingsUserActionTracker(const SettingsUserActionTracker& other) = delete;
@@ -33,8 +31,7 @@
   ~SettingsUserActionTracker() override;
 
   void BindInterface(
-      mojo::PendingReceiver<ash::settings::mojom::UserActionRecorder>
-          pending_receiver);
+      mojo::PendingReceiver<mojom::UserActionRecorder> pending_receiver);
 
  private:
   // For unit tests.
@@ -61,8 +58,8 @@
   void RecordSearch() override;
   void RecordSettingChange() override;
   void RecordSettingChangeWithDetails(
-      mojom::Setting setting,
-      ash::settings::mojom::SettingChangeValuePtr value) override;
+      chromeos::settings::mojom::Setting setting,
+      mojom::SettingChangeValuePtr value) override;
 
   void EndCurrentSession();
   void OnBindingDisconnected();
@@ -71,10 +68,9 @@
   OsSettingsSections* sections_;
 
   std::unique_ptr<PerSessionSettingsUserActionTracker> per_session_tracker_;
-  mojo::Receiver<ash::settings::mojom::UserActionRecorder> receiver_{this};
+  mojo::Receiver<mojom::UserActionRecorder> receiver_{this};
 };
 
-}  // namespace settings
-}  // namespace chromeos
+}  // namespace ash::settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_ASH_SETTINGS_USER_ACTION_TRACKER_H_
diff --git a/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker_unittest.cc b/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker_unittest.cc
index 2059ae9..5bba536 100644
--- a/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker_unittest.cc
+++ b/chrome/browser/ui/webui/settings/ash/settings_user_action_tracker_unittest.cc
@@ -14,13 +14,12 @@
 #include "chrome/browser/ui/webui/settings/chromeos/constants/setting.mojom.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-namespace chromeos {
-namespace settings {
+namespace ash::settings {
 
-// TODO(https://crbug.com/1164001): remove after migrating to ash.
 namespace mojom {
-using ::ash::settings::mojom::SettingChangeValue;
-}
+using ::chromeos::settings::mojom::Section;
+using ::chromeos::settings::mojom::Setting;
+}  // namespace mojom
 
 class SettingsUserActionTrackerTest : public testing::Test {
  protected:
@@ -190,5 +189,4 @@
               mojom::Setting::kScanningApp);
 }
 
-}  // namespace settings.
-}  // namespace chromeos.
+}  // namespace ash::settings
diff --git a/chrome/browser/ui/webui/settings/chromeos/constants/constants_util.h b/chrome/browser/ui/webui/settings/chromeos/constants/constants_util.h
index 0d4929c..64af7fe 100644
--- a/chrome/browser/ui/webui/settings/chromeos/constants/constants_util.h
+++ b/chrome/browser/ui/webui/settings/chromeos/constants/constants_util.h
@@ -22,4 +22,11 @@
 }  // namespace settings
 }  // namespace chromeos
 
+// TODO(https://crbug.com/1164001): remove when it moved to ash.
+namespace ash::settings::constants {
+using ::chromeos::settings::constants::AllSections;
+using ::chromeos::settings::constants::AllSettings;
+using ::chromeos::settings::constants::AllSubpages;
+}  // namespace ash::settings::constants
+
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_CONSTANTS_CONSTANTS_UTIL_H_