[waffle]Remove the 'ENABLE_SEARCH_ENGINE_CHOICE' build flag

We remove the buildflag because it has caused a lot of issues when
we forget to check if the code compiles on Fuchsia for example.

Instead, we build the files on all Desktop operating systems and
make sure that the `SearchEngineChoiceService` is only initialized
on the operating systems in which we want to display the screen.

Fixed: b:308433630
Change-Id: I4c582cc060050c2986144af9c38b34aadf37a57b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5110204
Reviewed-by: Kinuko Yasuda <[email protected]>
Auto-Submit: Jack Yammine <[email protected]>
Reviewed-by: David Roger <[email protected]>
Code-Coverage: [email protected] <[email protected]>
Reviewed-by: Colin Blundell <[email protected]>
Commit-Queue: Jack Yammine <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1238394}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index 9d11d79..3bb3c80 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -165,7 +165,6 @@
 #include "components/services/screen_ai/buildflags/buildflags.h"
 #include "components/services/storage/public/cpp/storage_prefs.h"
 #include "components/sessions/core/session_id_generator.h"
-#include "components/signin/public/base/signin_buildflags.h"
 #include "components/signin/public/base/signin_pref_names.h"
 #include "components/signin/public/identity_manager/identity_manager.h"
 #include "components/site_engagement/content/site_engagement_service.h"
@@ -230,13 +229,6 @@
 #endif  // BUILDFLAG(IS_CHROMEOS_ASH)
 #endif  // BUILDFLAG(ENABLE_EXTENSIONS)
 
-// `search_engine_choice_service.h` includes `chrome/browser/ui/browser_list.h`
-// that can't be included on android.
-#if BUILDFLAG(ENABLE_SEARCH_ENGINE_CHOICE)
-#include "chrome/browser/search_engine_choice/search_engine_choice_client_side_trial.h"
-#include "chrome/browser/search_engine_choice/search_engine_choice_service.h"
-#endif
-
 #if BUILDFLAG(ENABLE_PDF)
 #include "chrome/browser/pdf/pdf_pref_names.h"
 #endif  // BUILDFLAG(ENABLE_PDF)
@@ -292,6 +284,8 @@
 #include "chrome/browser/new_tab_page/promos/promo_service.h"
 #include "chrome/browser/policy/developer_tools_policy_handler.h"
 #include "chrome/browser/search/background/ntp_custom_background_service.h"
+#include "chrome/browser/search_engine_choice/search_engine_choice_client_side_trial.h"
+#include "chrome/browser/search_engine_choice/search_engine_choice_service.h"
 #include "chrome/browser/serial/serial_policy_allowed_ports.h"
 #include "chrome/browser/signin/signin_promo.h"
 #include "chrome/browser/ui/commerce/commerce_ui_tab_helper.h"
@@ -1479,6 +1473,8 @@
   metrics::TabStatsTracker::RegisterPrefs(registry);
   performance_manager::user_tuning::prefs::RegisterLocalStatePrefs(registry);
   RegisterBrowserPrefs(registry);
+  SearchEngineChoiceService::RegisterLocalStatePrefs(registry);
+  SearchEngineChoiceClientSideTrial::RegisterLocalStatePrefs(registry);
   speech::SodaInstaller::RegisterLocalStatePrefs(registry);
   StartupBrowserCreator::RegisterLocalStatePrefs(registry);
   task_manager::TaskManagerInterface::RegisterPrefs(registry);
@@ -1625,11 +1621,6 @@
   PlatformAuthPolicyObserver::RegisterPrefs(registry);
 #endif  // BUILDFLAG(IS_WIN)
 
-#if BUILDFLAG(ENABLE_SEARCH_ENGINE_CHOICE)
-  SearchEngineChoiceService::RegisterLocalStatePrefs(registry);
-  SearchEngineChoiceClientSideTrial::RegisterLocalStatePrefs(registry);
-#endif
-
   // Platform-specific and compile-time conditional individual preferences.
   // If you have multiple preferences that should clearly be grouped together,
   // please group them together into a helper function called above. Please