Add flag to track migration from email to gaia id.

components/signin/core/browser/account_tracker_service.h

Index: components/signin/core/browser/account_tracker_service.h
diff --git a/components/signin/core/browser/account_tracker_service.h b/components/signin/core/browser/account_tracker_service.h
index 36c8b8578dfc3d146c7eee2849693cb07e079cd9..62b78039d1190395a8ebde0ca9360a8be2b604a1 100644
--- a/components/signin/core/browser/account_tracker_service.h
+++ b/components/signin/core/browser/account_tracker_service.h
@@ -48,6 +48,13 @@ class AccountTrackerService : public KeyedService,
     virtual void OnAccountRemoved(const AccountInfo& info) = 0;
   };
 
+  // Possible values for the kAccountIdMigrationState preference.
+  enum AccountIdMigrationState {
+    MIGRATION_NOT_STARTED,
+    MIGRATION_IN_PROGRESS,
+    MIGRATION_DONE
+  };
+
   AccountTrackerService();
   virtual ~AccountTrackerService();
 
@@ -72,6 +79,9 @@ class AccountTrackerService : public KeyedService,
   // there are still unfininshed fetchers.
   virtual bool IsAllUserInfoFetched() const;
 
+  AccountIdMigrationState GetMigrationState();
+  static AccountIdMigrationState GetMigrationState(PrefService* pref_service);
+
  private:
   friend class AccountInfoFetcher;