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

components/sync/engine_impl/sync_manager_impl.h

 // Copyright 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_SYNC_MANAGER_IMPL_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_SYNC_MANAGER_IMPL_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 113 matching lines @@
   void OnPassphraseTypeChanged(PassphraseType type,
                                base::Time explicit_passphrase_time) override;
   void OnLocalSetPassphraseEncryption(
       const SyncEncryptionHandler::NigoriState& nigori_state) 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;
 
   // ServerConnectionEventListener implementation.
   void OnServerConnectionEvent(const ServerConnectionEvent& event) override;
 
   // JsBackend implementation.
   void SetJsEventHandler(
       const WeakHandle<JsEventHandler>& event_handler) override;
 
@@ skipping 189 matching lines @@
   std::unique_ptr<SyncEncryptionHandlerImpl> sync_encryption_handler_;
 
   base::WeakPtrFactory<SyncManagerImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncManagerImpl);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_SYNC_MANAGER_IMPL_H_