[Sync] Remove unneeded 'using syncer::' lines and 'syncer::' scopings

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_
 
 #include "base/compiler_specific.h"
 #include "sync/engine/syncer_command.h"
 #include "sync/internal_api/public/engine/model_safe_worker.h"
@@ skipping 12 matching lines @@
 // SyncerCommand whenever the operation might change any client-visible
 // fields on any syncable::Entry.  If the operation involves creating a
 // WriteTransaction, this is a sign that ModelChangingSyncerCommand is likely
 // necessary.
 class ModelChangingSyncerCommand : public SyncerCommand {
  public:
   ModelChangingSyncerCommand() : work_session_(NULL) { }
   virtual ~ModelChangingSyncerCommand() { }
 
   // SyncerCommand implementation. Sets work_session to session.
-  virtual syncer::SyncerError ExecuteImpl(
-      sessions::SyncSession* session) OVERRIDE;
+  virtual SyncerError ExecuteImpl(sessions::SyncSession* session) OVERRIDE;
 
   // Wrapper so implementations don't worry about storing work_session.
   SyncerError StartChangingModel() {
     return ModelChangingExecuteImpl(work_session_);
   }
 
   std::set<ModelSafeGroup> GetGroupsToChangeForTest(
       const sessions::SyncSession& session) const {
     return GetGroupsToChange(session);
   }
@@ skipping 22 matching lines @@
   // 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 syncer
 
 #endif  // SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_