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..87a341c8e1d690b945b119337e430a6974c8c957 100644
--- a/Source/modules/gamepad/WebKitGamepadList.h
+++ b/Source/modules/gamepad/WebKitGamepadList.h
@@ -7,6 +7,7 @@
 
 #include "bindings/v8/ScriptWrappable.h"
 #include "heap/Handle.h"
+#include "modules/gamepad/Gamepad.h"
 #include "modules/gamepad/WebKitGamepad.h"
 #include "public/platform/WebGamepads.h"
 #include "wtf/PassRefPtr.h"
@@ -15,23 +16,22 @@
 
 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); }
-    ~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() { ScriptWrappable::init(this); }
     RefPtrWillBeMember<WebKitGamepad> m_items[blink::WebGamepads::itemsLengthCap];
 };