Update Gamepad.axes / GamepadButton.value to match the latest specification

Source/modules/gamepad/GamepadButton.h

 // 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.
 
 #ifndef GamepadButton_h
 #define GamepadButton_h
 
 #include "bindings/v8/ScriptWrappable.h"
 #include "platform/heap/Handle.h"
 #include "wtf/RefCounted.h"
 #include "wtf/Vector.h"
 
 namespace WebCore {
 
 class GamepadButton FINAL : public GarbageCollectedFinalized<GamepadButton>, public ScriptWrappable {
 public:
     static GamepadButton* create();
     ~GamepadButton();
 
-    float value() const { return m_value; }
-    void setValue(float val) { m_value = val; }
+    double value() const { return m_value; }
+    void setValue(double val) { m_value = val; }
 
     bool pressed() const { return m_pressed; }
     void setPressed(bool val) { m_pressed = val; }
 
     void trace(Visitor*);
 
 private:
     GamepadButton();
-    float m_value;
+    double m_value;
     bool m_pressed;
 };
 
 typedef HeapVector<Member<GamepadButton> > GamepadButtonVector;
 
 } // namespace WebCore
 
 #endif // GamepadButton_h