Factor out GamepadCommon base class from Gamepad and WebKitGamepad

Source/modules/gamepad/WebKitGamepadList.cpp

Index: Source/modules/gamepad/WebKitGamepadList.cpp
diff --git a/Source/modules/gamepad/WebKitGamepadList.cpp b/Source/modules/gamepad/WebKitGamepadList.cpp
index da3cec035cfa7c6f3c9422ced08e90c92eb9dedf..e9105db39e89b53a2bc18089bfb2139b79012077 100644
--- a/Source/modules/gamepad/WebKitGamepadList.cpp
+++ b/Source/modules/gamepad/WebKitGamepadList.cpp
@@ -7,6 +7,11 @@
 
 namespace WebCore {
 
+WebKitGamepadList::WebKitGamepadList()
+{
+    ScriptWrappable::init(this);
+}
+
 WebKitGamepadList::~WebKitGamepadList()
 {
 }
@@ -18,11 +23,6 @@ void WebKitGamepadList::set(unsigned index, PassRefPtrWillBeRawPtr<WebKitGamepad
     m_items[index] = gamepad;
 }
 
-unsigned WebKitGamepadList::length() const
-{
-    return blink::WebGamepads::itemsLengthCap;
-}
-
 WebKitGamepad* WebKitGamepadList::item(unsigned index)
 {
     return index < length() ? m_items[index].get() : 0;