Add chrome://flags entry for account-scoped preferences

This CL adds a chrome://flags entry for
syncer::kEnablePreferencesAccountStorage (for both iOS and other
platforms).

Bug: 1416480
Change-Id: I7b931ff56f300fef83ff3ffd0d2ba6b4b73885ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4334360
Reviewed-by: Maksim Moskvitin <[email protected]>
Commit-Queue: Marc Treib <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1116868}
diff --git a/ios/chrome/browser/flags/about_flags.mm b/ios/chrome/browser/flags/about_flags.mm
index 193d647..af61c18 100644
--- a/ios/chrome/browser/flags/about_flags.mm
+++ b/ios/chrome/browser/flags/about_flags.mm
@@ -1442,6 +1442,11 @@
      flags_ui::kOsIos,
      FEATURE_VALUE_TYPE(
          autofill::features::kAutofillUpstreamAuthenticatePreflightCall)},
+    {"enable-preferences-account-storage",
+     flag_descriptions::kEnablePreferencesAccountStorageName,
+     flag_descriptions::kEnablePreferencesAccountStorageDescription,
+     flags_ui::kOsIos,
+     FEATURE_VALUE_TYPE(syncer::kEnablePreferencesAccountStorage)},
 };
 
 bool SkipConditionalFeatureEntry(const flags_ui::FeatureEntry& entry) {