Add isHTMLPlugInElement() helpers for consistency with other HTML elements

Source/core/dom/Node.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * 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 227 matching lines @@
             : NotCustomElement;
     }
     void setCustomElementState(CustomElementState newState);
 
     virtual bool isMediaControlElement() const { return false; }
     virtual bool isMediaControls() const { return false; }
     virtual bool isVTTElement() const { return false; }
     virtual bool isAttributeNode() const { return false; }
     virtual bool isCharacterDataNode() const { return false; }
     virtual bool isFrameOwnerElement() const { return false; }
-    virtual bool isPluginElement() const { return false; }
 
     // StyledElements allow inline style (style="border: 1px"), presentational attributes (ex. color),
     // class names (ex. class="foo bar") and other non-basic styling features. They and also control
     // if this element can participate in style sharing.
     //
     // FIXME: The only things that ever go through StyleResolver that aren't StyledElements are
     // PseudoElements and VTTElements. It's possible we can just eliminate all the checks
     // since those elements will never have class names, inline style, or other things that
     // this apparently guards against.
     bool isStyledElement() const { return isHTMLElement() || isSVGElement(); }
@@ skipping 649 matching lines @@
 } // namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showNode(const WebCore::Node*);
 void showTree(const WebCore::Node*);
 void showNodePath(const WebCore::Node*);
 #endif
 
 #endif