Implement contextmenu attribute with basic support of <menu>

Source/core/page/ContextMenuController.h

Index: Source/core/page/ContextMenuController.h
diff --git a/Source/core/page/ContextMenuController.h b/Source/core/page/ContextMenuController.h
index 5ea8a9c90be089a3e6c53368ecf4f0fb468e88eb..481e8c40d7d58cb2fa7c8015ff0b2b13f545882e 100644
--- a/Source/core/page/ContextMenuController.h
+++ b/Source/core/page/ContextMenuController.h
@@ -40,6 +40,8 @@ namespace blink {
     class ContextMenuProvider;
     class Document;
     class Event;
+    class HTMLElement;

[tkent, 2014/08/05 02:33:23]

This is unnecessary.

+    class HTMLMenuElement;

[tkent, 2014/08/05 02:33:23]

Ditto.

     class LocalFrame;
     class Page;
 
@@ -68,6 +70,7 @@ namespace blink {
 
         PassOwnPtr<ContextMenu> createContextMenu(Event*);
         PassOwnPtr<ContextMenu> createContextMenu(LocalFrame*, const LayoutPoint&);
+        void populateCustomContextMenu(Event*);
         void showContextMenu(Event*);
 
         ContextMenuClient* m_client;