[Sync] Make syncer commands avoid posting tasks on threads with no work to do

chrome/browser/sync/engine/process_commit_response_command.h

 // Copyright (c) 2011 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 CHROME_BROWSER_SYNC_ENGINE_PROCESS_COMMIT_RESPONSE_COMMAND_H_
 #define CHROME_BROWSER_SYNC_ENGINE_PROCESS_COMMIT_RESPONSE_COMMAND_H_
 #pragma once
 
 #include <set>
 #include <string>
@@ skipping 10 matching lines @@
 }
 
 namespace browser_sync {
 
 class ProcessCommitResponseCommand : public ModelChangingSyncerCommand {
  public:
 
   ProcessCommitResponseCommand();
   virtual ~ProcessCommitResponseCommand();
 
+ protected:
   // ModelChangingSyncerCommand implementation.
-  virtual bool ModelNeutralExecuteImpl(sessions::SyncSession* session) OVERRIDE;
+  virtual std::set<ModelSafeGroup> GetGroupsToChange(
+      const sessions::SyncSession& session) const OVERRIDE;
+  virtual bool ModelNeutralExecuteImpl(
+      sessions::SyncSession* session) OVERRIDE;
   virtual void ModelChangingExecuteImpl(
       sessions::SyncSession* session) OVERRIDE;
 
  private:
   CommitResponse::ResponseType ProcessSingleCommitResponse(
       syncable::WriteTransaction* trans,
       const sync_pb::CommitResponse_EntryResponse& pb_commit_response,
       const sync_pb::SyncEntity& pb_committed_entry,
       const syncable::Id& pre_commit_id,
       std::set<syncable::Id>* conflicting_new_directory_ids,
@@ skipping 45 matching lines @@
   const std::string& GetResultingPostCommitName(
       const sync_pb::SyncEntity& committed_entry,
       const CommitResponse_EntryResponse& entry_response);
 
   DISALLOW_COPY_AND_ASSIGN(ProcessCommitResponseCommand);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_ENGINE_PROCESS_COMMIT_RESPONSE_COMMAND_H_