Add isTabStop attribute to Element

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index 3a79335f875c4b1ca9768b3ffedc51ff87e52c34..158496baa792114a16c091d6ef0481b835d623c2 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -374,6 +374,8 @@ public:
     virtual bool supportsFocus() const;
     // Whether the node can actually be focused.
     bool isFocusable() const;
+    bool isTabStop() const;
+    void setIsTabStop(bool);
     virtual bool isKeyboardFocusable() const;
     virtual bool isMouseFocusable() const;
     virtual void dispatchFocusEvent(Element* oldFocusedElement, WebFocusType);
@@ -648,6 +650,7 @@ private:
     v8::Handle<v8::Object> wrapCustomElement(v8::Isolate*, v8::Handle<v8::Object> creationContext);
 
     RefPtrWillBeMember<ElementData> m_elementData;
+    bool m_isTabStop;
 };
 
 DEFINE_NODE_TYPE_CASTS(Element, isElementNode());