Factor out GamepadCommon base class from Gamepad and WebKitGamepad

Source/modules/gamepad/WebKitGamepadList.h

Index: Source/modules/gamepad/WebKitGamepadList.h
diff --git a/Source/modules/gamepad/WebKitGamepadList.h b/Source/modules/gamepad/WebKitGamepadList.h
index 574998ebdd6c65ed45ea86b2642878618ef07832..1f99ccb96dce9aa8c1366da4542e94d36f947831 100644
--- a/Source/modules/gamepad/WebKitGamepadList.h
+++ b/Source/modules/gamepad/WebKitGamepadList.h
@@ -15,23 +15,22 @@
 
 namespace WebCore {
 
-class WebKitGamepadList : public RefCountedWillBeGarbageCollectedFinalized<WebKitGamepadList>, public ScriptWrappable {
+class WebKitGamepadList FINAL : public RefCountedWillBeGarbageCollectedFinalized<WebKitGamepadList>, public ScriptWrappable {
 public:
-    static PassRefPtrWillBeRawPtr<WebKitGamepadList> create() { return adoptRefWillBeNoop(new WebKitGamepadList); }
+    static PassRefPtrWillBeRawPtr<WebKitGamepadList> create()
+    {
+        return adoptRefWillBeNoop(new WebKitGamepadList);
+    }
     ~WebKitGamepadList();
 
     void set(unsigned index, PassRefPtrWillBeRawPtr<WebKitGamepad>);
     WebKitGamepad* item(unsigned index);
-    unsigned length() const;
+    unsigned length() const { return blink::WebGamepads::itemsLengthCap; }
 
     void trace(Visitor*);
 
 private:
-    WebKitGamepadList()
-    {
-        ScriptWrappable::init(this);
-    }
-
+    WebKitGamepadList();
     RefPtrWillBeMember<WebKitGamepad> m_items[blink::WebGamepads::itemsLengthCap];
 };