Change WebCore namespace to blink

Source/modules/gamepad/GamepadButton.cpp

 // Copyright 2014 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.
 
 #include "config.h"
 #include "modules/gamepad/Gamepad.h"
 
 namespace blink {
 
 GamepadButton* GamepadButton::create()
 {
     return new GamepadButton();
 }
 
 GamepadButton::GamepadButton()
     : m_value(0.)
     , m_pressed(false)
 {
     ScriptWrappable::init(this);
 }
 
-} // namespace WebCore
+} // namespace blink