Implement contextmenu attribute with basic support of <menu>

Source/core/html/HTMLElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004-2008, 2013, 2014 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2011 Motorola Mobility. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 30 matching lines @@
 #include "core/dom/Text.h"
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/editing/markup.h"
 #include "core/events/EventListener.h"
 #include "core/events/KeyboardEvent.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLBRElement.h"
 #include "core/html/HTMLFormElement.h"
 #include "core/html/HTMLInputElement.h"
+#include "core/html/HTMLMenuElement.h"
 #include "core/html/HTMLTemplateElement.h"
 #include "core/html/HTMLTextFormControlElement.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/rendering/RenderObject.h"
 #include "platform/text/BidiResolver.h"
 #include "platform/text/BidiTextRun.h"
 #include "platform/text/TextRunIterator.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/text/CString.h"
 
@@ skipping 832 matching lines @@
         parsedColor.setRGB(parseColorStringWithCrazyLegacyRules(colorString));
 
     style->setProperty(propertyID, cssValuePool().createColorValue(parsedColor.rgb()));
 }
 
 bool HTMLElement::isInteractiveContent() const
 {
     return false;
 }
 
+HTMLMenuElement* HTMLElement::menuElement() const
+{
+    Element* element = treeScope().getElementById(fastGetAttribute(contextmenuAttr));
+    return isHTMLMenuElement(element) ? toHTMLMenuElement(element) : 0;
+}
+
 void HTMLElement::defaultEventHandler(Event* event)
 {
     if (event->type() == EventTypeNames::keypress && event->isKeyboardEvent()) {
         handleKeypressEvent(toKeyboardEvent(event));
         if (event->defaultHandled())
             return;
     }
 
     Element::defaultEventHandler(event);
 }
@@ skipping 45 matching lines @@
 #ifndef NDEBUG
 
 // For use in the debugger
 void dumpInnerHTML(blink::HTMLElement*);
 
 void dumpInnerHTML(blink::HTMLElement* element)
 {
     printf("%s\n", element->innerHTML().ascii().data());
 }
 #endif