[SyncFS] Add ScopedEnableSyncFSV2 for testing

chrome/browser/sync_file_system/syncable_file_system_util.h

 // Copyright 2013 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_FILE_SYSTEM_SYNCABLE_FILE_SYSTEM_UTIL_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNCABLE_FILE_SYSTEM_UTIL_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 97 matching lines @@
  public:
   ScopedEnableSyncFSDirectoryOperation();
   ~ScopedEnableSyncFSDirectoryOperation();
 
  private:
   bool was_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedEnableSyncFSDirectoryOperation);
 };
 
+// Enables V2 backend for syncable filesystems temporarily for testing.
+class ScopedEnableSyncFSV2 {
+ public:
+  ScopedEnableSyncFSV2();
+  ~ScopedEnableSyncFSV2();
+
+ private:
+  bool was_enabled_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedEnableSyncFSV2);
+};
+
 // Posts |callback| to the current thread.
 void RunSoon(const tracked_objects::Location& from_here,
              const base::Closure& callback);
 
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNCABLE_FILE_SYSTEM_UTIL_H_