Refactoring: Add convenience method toPluginContainerImpl.

Source/web/WebNode.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 225 matching lines @@
 WebPluginContainer* WebNode::pluginContainer() const
 {
     if (isNull())
         return 0;
     const Node* coreNode = constUnwrap<Node>();
     if (coreNode->hasTagName(HTMLNames::objectTag) || coreNode->hasTagName(HTMLNames::embedTag)) {
         RenderObject* object = coreNode->renderer();
         if (object && object->isWidget()) {
             Widget* widget = WebCore::toRenderWidget(object)->widget();
             if (widget && widget->isPluginContainer())
-                return static_cast<WebPluginContainerImpl*>(widget);
+                return toPluginContainerImpl(widget);
         }
     }
     return 0;
 }
 
 WebElement WebNode::shadowHost() const
 {
     if (isNull())
         return WebElement();
     const Node* coreNode = constUnwrap<Node>();
@@ skipping 10 matching lines @@
     m_private = node;
     return *this;
 }
 
 WebNode::operator PassRefPtr<Node>() const
 {
     return m_private.get();
 }
 
 } // namespace WebKit