Add flag to track migration from email to gaia id.

components/signin/core/browser/account_tracker_service.cc

Index: components/signin/core/browser/account_tracker_service.cc
diff --git a/components/signin/core/browser/account_tracker_service.cc b/components/signin/core/browser/account_tracker_service.cc
index 4f205bf7018a14f2f82dfd5634093a73c5873312..ae4ae9b313c0bb44231543f6e4ce48f63e9a3d8c 100644
--- a/components/signin/core/browser/account_tracker_service.cc
+++ b/components/signin/core/browser/account_tracker_service.cc
@@ -9,6 +9,7 @@
 #include "base/prefs/scoped_user_pref_update.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/signin/core/browser/signin_manager.h"
+#include "components/signin/core/common/signin_pref_names.h"
 #include "google_apis/gaia/gaia_auth_util.h"
 #include "google_apis/gaia/gaia_constants.h"
 #include "google_apis/gaia/gaia_oauth_client.h"
@@ -242,6 +243,18 @@ AccountTrackerService::FindAccountInfoByEmail(
   return AccountInfo();
 }
 
+AccountTrackerService::AccountIdMigrationState
+AccountTrackerService::GetMigrationState() {
+  return GetMigrationState(pref_service_);
+}
+
+// static
+AccountTrackerService::AccountIdMigrationState
+AccountTrackerService::GetMigrationState(PrefService* pref_service) {
+  return static_cast<AccountTrackerService::AccountIdMigrationState>(
+      pref_service->GetInteger(prefs::kAccountIdMigrationState));
+}
+
 void AccountTrackerService::OnRefreshTokenAvailable(
     const std::string& account_id) {
   TRACE_EVENT1("AccountTrackerService",