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

components/sync/engine_impl/get_updates_processor.cc

 // Copyright 2014 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/engine_impl/get_updates_processor.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 58 matching lines @@
   for (int i = 0; i < update_count; ++i) {
     const sync_pb::SyncEntity& update = gu_response.entries(i);
     ModelType type = GetModelType(update);
     if (!IsRealDataType(type)) {
       NOTREACHED() << "Received update with invalid type.";
       continue;
     }
 
     TypeSyncEntityMap::iterator it = updates_by_type->find(type);
     if (it == updates_by_type->end()) {
-      DLOG(WARNING)
-          << "Received update for unexpected type or the type is throttled:"
-          << ModelTypeToString(type);
+      DLOG(WARNING) << "Received update for unexpected type, or the type is "
+                       "throttled or failed with partial failure:"
+                    << ModelTypeToString(type);
       continue;
     }
 
     it->second.push_back(&update);
   }
 }
 
 // Builds a map of ModelTypes to indices to progress markers in the given
 // |gu_response| message.  The map is returned in the |index_map| parameter.
 void PartitionProgressMarkersByType(
@@ skipping 268 matching lines @@
 }
 
 void GetUpdatesProcessor::CopyClientDebugInfo(
     DebugInfoGetter* debug_info_getter,
     sync_pb::DebugInfo* debug_info) {
   DVLOG(1) << "Copying client debug info to send.";
   debug_info_getter->GetDebugInfo(debug_info);
 }
 
 }  // namespace syncer