Refactoring: Add convenience method toPluginContainerImpl.

Source/web/ChromeClientImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  *
  * 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.
@@ skipping 568 matching lines @@
     // Find out if the mouse is over a link, and if so, let our UI know...
     if (result.isLiveLink() && !result.absoluteLinkURL().string().isEmpty())
         url = result.absoluteLinkURL();
     else if (result.innerNonSharedNode()
              && (result.innerNonSharedNode()->hasTagName(HTMLNames::objectTag)
                  || result.innerNonSharedNode()->hasTagName(HTMLNames::embedTag))) {
         RenderObject* object = result.innerNonSharedNode()->renderer();
         if (object && object->isWidget()) {
             Widget* widget = toRenderWidget(object)->widget();
             if (widget && widget->isPluginContainer()) {
-                WebPluginContainerImpl* plugin = static_cast<WebPluginContainerImpl*>(widget);
+                WebPluginContainerImpl* plugin = toPluginContainerImpl(widget);
                 url = plugin->plugin()->linkAtPosition(result.roundedPointInInnerNodeFrame());
             }
         }
     }
 
     m_webView->client()->setMouseOverURL(url);
 }
 
 void ChromeClientImpl::setToolTip(const String& tooltipText, TextDirection dir)
 {
@@ skipping 416 matching lines @@
 {
 }
 
 void NavigatorContentUtilsClientImpl::registerProtocolHandler(const String& scheme, const String& baseURL, const String& url, const String& title)
 {
     m_webView->client()->registerProtocolHandler(scheme, baseURL, url, title);
 }
 #endif
 
 } // namespace WebKit