Factor out GamepadCommon base class from Gamepad and WebKitGamepad

Source/modules/gamepad/GamepadList.cpp

Index: Source/modules/gamepad/GamepadList.cpp
diff --git a/Source/modules/gamepad/GamepadList.cpp b/Source/modules/gamepad/GamepadList.cpp
index cc29a73dbbddb90c0752ee0f7d3cb8edc4f7e3c5..376e2f17feca130ba8de2a41e9fc675ff81d62e6 100644
--- a/Source/modules/gamepad/GamepadList.cpp
+++ b/Source/modules/gamepad/GamepadList.cpp
@@ -28,6 +28,11 @@
 
 namespace WebCore {
 
+GamepadList::GamepadList()
+{
+    ScriptWrappable::init(this);
+}
+
 GamepadList::~GamepadList()
 {
 }
@@ -39,11 +44,6 @@ void GamepadList::set(unsigned index, PassRefPtrWillBeRawPtr<Gamepad> gamepad)
     m_items[index] = gamepad;
 }
 
-unsigned GamepadList::length() const
-{
-    return blink::WebGamepads::itemsLengthCap;
-}
-
 Gamepad* GamepadList::item(unsigned index)
 {
     return index < length() ? m_items[index].get() : 0;