Switch the inheritance of WebView from WebWidget to protected.

third_party/WebKit/Source/web/WebViewImpl.h

 /*
  * Copyright (C) 2010 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 737 matching lines @@
     WebPageImportanceSignals m_pageImportanceSignals;
 
     const OwnPtr<WebViewScheduler> m_scheduler;
 
     // Manages the layer tree created for this page in Slimming Paint v2.
     PaintArtifactCompositor m_paintArtifactCompositor;
 
     double m_lastFrameTimeMonotonic;
 };
 
-DEFINE_TYPE_CASTS(WebViewImpl, WebWidget, widget, widget->isWebView(), widget.isWebView());
 // We have no ways to check if the specified WebView is an instance of
 // WebViewImpl because WebViewImpl is the only implementation of WebView.
 DEFINE_TYPE_CASTS(WebViewImpl, WebView, webView, true, true);
 
 } // namespace blink
 
 #endif