Add Mac implementation of data_fetcher for gamepad.

content/browser/gamepad/data_fetcher.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 CONTENT_BROWSER_GAMEPAD_DATA_FETCHER_H_
 #define CONTENT_BROWSER_GAMEPAD_DATA_FETCHER_H_
 
 namespace WebKit {
 class WebGamepads;
 }
 
 namespace content {
 
 class GamepadDataFetcher {
  public:
   virtual ~GamepadDataFetcher() {}
   virtual void GetGamepadData(WebKit::WebGamepads* pads,
                               bool devices_changed_hint) = 0;
+  virtual void PauseHint(bool paused) {}
 };
 
 } // namespace content
 
 #endif  // CONTENT_BROWSER_GAMEPAD_DATA_FETCHER_H_