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

components/sync/engine/sync_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_SYNC_STATUS_H_
 #define COMPONENTS_SYNC_ENGINE_SYNC_STATUS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 63 matching lines @@
   ModelTypeSet encrypted_types;
   bool cryptographer_ready;
   bool crypto_has_pending_keys;
   bool has_keystore_key;
   base::Time keystore_migration_time;
   PassphraseType passphrase_type;
 
   // Per-datatype throttled status.
   ModelTypeSet throttled_types;
 
+  // Per-datatype backed off status.
+  ModelTypeSet backed_off_types;
+
   // The unique identifer for the sync store.
   std::string sync_id;
 
   // The unique identifier for the invalidation client.
   std::string invalidator_client_id;
 
   // Counters grouped by model type
   std::vector<int> num_entries_by_type;
   std::vector<int> num_to_delete_entries_by_type;
 
   // Time of next retry if sync scheduler is throttled or in backoff.
   base::Time retry_time;
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_SYNC_STATUS_H_