[Sync] Sync client should to exponential backoff when receive partial failure

components/sync/test/engine/fake_sync_scheduler.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/sync/test/engine/fake_sync_scheduler.h"
 
 namespace syncer {
 
 FakeSyncScheduler::FakeSyncScheduler() {}
 
@@ skipping 32 matching lines @@
 void FakeSyncScheduler::OnCredentialsUpdated() {}
 
 void FakeSyncScheduler::OnConnectionStatusChange() {}
 
 void FakeSyncScheduler::OnThrottled(const base::TimeDelta& throttle_duration) {}
 
 void FakeSyncScheduler::OnTypesThrottled(
     ModelTypeSet types,
     const base::TimeDelta& throttle_duration) {}
 
+void FakeSyncScheduler::OnTypesBackedOff(ModelTypeSet types) {}
+
 bool FakeSyncScheduler::IsCurrentlyThrottled() {
   return false;
 }
 
 void FakeSyncScheduler::OnReceivedShortPollIntervalUpdate(
     const base::TimeDelta& new_interval) {}
 
 void FakeSyncScheduler::OnReceivedLongPollIntervalUpdate(
     const base::TimeDelta& new_interval) {}
 
 void FakeSyncScheduler::OnReceivedCustomNudgeDelays(
     const std::map<ModelType, base::TimeDelta>& nudge_delays) {}
 
 void FakeSyncScheduler::OnReceivedClientInvalidationHintBufferSize(int size) {}
 
 void FakeSyncScheduler::OnSyncProtocolError(const SyncProtocolError& error) {}
 
 void FakeSyncScheduler::OnReceivedGuRetryDelay(const base::TimeDelta& delay) {}
 
 void FakeSyncScheduler::OnReceivedMigrationRequest(ModelTypeSet types) {}
 
 }  // namespace syncer