Implement contextmenu attribute with basic support of <menu>

Source/core/html/HTMLElement.h

Index: Source/core/html/HTMLElement.h
diff --git a/Source/core/html/HTMLElement.h b/Source/core/html/HTMLElement.h
index 717a6085c2fa05e974f52bd1dff584fccb2440fc..1fcf07722ef297140ada04301994a6cdde4ebfa1 100644
--- a/Source/core/html/HTMLElement.h
+++ b/Source/core/html/HTMLElement.h
@@ -30,6 +30,7 @@ namespace blink {
 class DocumentFragment;
 class HTMLCollection;
 class HTMLFormElement;
+class HTMLMenuElement;
 class ExceptionState;
 
 enum TranslateAttributeMode {
@@ -95,6 +96,8 @@ public:
 
     static const AtomicString& eventParameterName();
 
+    HTMLMenuElement* menuElement() const;

[tkent, 2014/07/25 04:42:38]

HTMLMenuElement dependency from HTMLElement is weird.
ContextMenuProvider should have this.

[tkent, 2014/07/25 04:46:58]

Please ignore this comment.

Instead, this function should be renamed to |contextMenu|, and exposed via IDL.

[pals, 2014/07/30 09:47:43]

Done.

+
 protected:
     HTMLElement(const QualifiedName& tagName, Document&, ConstructionType);