Cleanup: Remove unnecessary code related to PagePopupDriver.

Source/web/ChromeClientImpl.h

 /*
  * 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 172 matching lines @@
 private:
     bool isChromeClientImpl() const override { return true; }
     void registerPopupOpeningObserver(PopupOpeningObserver*) override;
     void unregisterPopupOpeningObserver(PopupOpeningObserver*) override;
 
     void notifyPopupOpeningObservers() const;
     void setCursor(const WebCursorInfo&);
 
     WebViewImpl* m_webView;  // weak pointer
     WindowFeatures m_windowFeatures;
-
-    PagePopupDriver* m_pagePopupDriver;
     Vector<PopupOpeningObserver*> m_popupOpeningObservers;
 };
 
 DEFINE_TYPE_CASTS(ChromeClientImpl, ChromeClient, client, client->isChromeClientImpl(), client.isChromeClientImpl());
 
 } // namespace blink
 
 #endif