[passwords] Clean up UPM migration warning flag in activation algorithm

kUnifiedPasswordManagerLocalPasswordsMigrationWarning was *disabled* by
default in M132 (https://crrev.com/c/5928711, http://cl/686529557). It
can be cleaned up now.

Bug: 413696987
Change-Id: Ibbdbf67a959b2061f1490ea79e986909de4fba45
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6490857
Commit-Queue: Victor Vianna <[email protected]>
Reviewed-by: Maria Kazinova <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1452469}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index c409f160..412675b2 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -1091,6 +1091,12 @@
 inline constexpr char kManagedAccessToGetAllScreensMediaAllowedForUrls[] =
     "profile.managed_access_to_get_all_screens_media_allowed_for_urls";
 
+#if BUILDFLAG(IS_ANDROID)
+// Deprecated 04/2025.
+constexpr char kObsoleteUserAcknowledgedLocalPasswordsMigrationWarning[] =
+    "user_acknowledged_local_passwords_migration_warning";
+#endif
+
 // Register local state used only for migration (clearing or moving to a new
 // key).
 void RegisterLocalStatePrefsForMigration(PrefRegistrySimple* registry) {
@@ -1529,6 +1535,12 @@
 
   // Deprecated 04/2025.
   registry->RegisterListPref(kManagedAccessToGetAllScreensMediaAllowedForUrls);
+
+#if BUILDFLAG(IS_ANDROID)
+  // Deprecated 04/2025.
+  registry->RegisterBooleanPref(
+      kObsoleteUserAcknowledgedLocalPasswordsMigrationWarning, false);
+#endif
 }
 
 }  // namespace
@@ -2813,6 +2825,12 @@
   // Added 04/2025
   profile_prefs->ClearPref(kManagedAccessToGetAllScreensMediaAllowedForUrls);
 
+#if BUILDFLAG(IS_ANDROID)
+  // Added 04/2025
+  profile_prefs->ClearPref(
+      kObsoleteUserAcknowledgedLocalPasswordsMigrationWarning);
+#endif
+
   // Please don't delete the following line. It is used by PRESUBMIT.py.
   // END_MIGRATE_OBSOLETE_PROFILE_PREFS