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

components/sync/engine_impl/all_status.h

 // 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.
 
 #ifndef COMPONENTS_SYNC_ENGINE_IMPL_ALL_STATUS_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_ALL_STATUS_H_
 
 #include <map>
 #include <string>
 
@@ skipping 25 matching lines @@
 class AllStatus : public SyncEngineEventListener {
  public:
   AllStatus();
   ~AllStatus() override;
 
   // SyncEngineEventListener implementation.
   void OnSyncCycleEvent(const SyncCycleEvent& event) override;
   void OnActionableError(const SyncProtocolError& error) override;
   void OnRetryTimeChanged(base::Time retry_time) override;
   void OnThrottledTypesChanged(ModelTypeSet throttled_types) override;
+  void OnBackedOffTypesChanged(ModelTypeSet backed_off_types) override;
   void OnMigrationRequested(ModelTypeSet types) override;
   void OnProtocolEvent(const ProtocolEvent& event) override;
 
   SyncStatus status() const;
 
   void SetNotificationsEnabled(bool notifications_enabled);
 
   void IncrementNotifiableCommits();
 
   void IncrementNotificationsReceived();
@@ skipping 31 matching lines @@
   explicit ScopedStatusLock(AllStatus* allstatus);
   ~ScopedStatusLock();
 
  protected:
   AllStatus* allstatus_;
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_ALL_STATUS_H_