Refactor following sync commit loop change

sync/engine/model_changing_syncer_command.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 SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_
 #define SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "sync/engine/syncer_command.h"
@@ skipping 37 matching lines @@
   // This should return the set of groups in |session| that need to be
   // changed.  The returned set should be a subset of
   // session.GetEnabledGroups().  Subclasses can guarantee this either
   // by calling one of the session.GetEnabledGroups*() functions and
   // filtering that, or using GetGroupForModelType() (which handles
   // top-level/unspecified nodes) to project from model types to
   // groups.
   virtual std::set<ModelSafeGroup> GetGroupsToChange(
       const sessions::SyncSession& session) const = 0;
 
-  // Sometimes, a command has work to do that needs to touch global state
-  // belonging to multiple ModelSafeGroups, but in a way that is known to be
-  // safe.  This will be called once, prior to ModelChangingExecuteImpl,
-  // *without* a ModelSafeGroup restriction in place on the SyncSession.
-  // Returns true on success, false on failure.
-  // TODO(tim): Remove this (bug 36594).
-  virtual SyncerError ModelNeutralExecuteImpl(sessions::SyncSession* session);
-
   // Abstract method to be implemented by subclasses to handle logic that
   // operates on the model.  This is invoked with a SyncSession ModelSafeGroup
   // restriction in place so that bits of state belonging to data types
   // running on an unsafe thread are siloed away.
   virtual SyncerError ModelChangingExecuteImpl(
       sessions::SyncSession* session) = 0;
 
  private:
   // ExecuteImpl is expected to be run by SyncerCommand to set work_session.
   // StartChangingModel is called to start this command running.
   // Implementations will implement ModelChangingExecuteImpl and not
   // worry about storing the session or setting it. They are given work_session.
   sessions::SyncSession* work_session_;
 
   DISALLOW_COPY_AND_ASSIGN(ModelChangingSyncerCommand);
 };
 
 }  // namespace browser_sync
 
 #endif  // SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_