Implement top controls show/hide functionality for main thread scrolling

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 160 matching lines @@
     virtual void textFieldDataListChanged(HTMLInputElement&) override;
 
     virtual void didCancelCompositionOnSelectionChange() override;
     virtual void willSetInputMethodState() override;
     virtual void didUpdateTextOfFocusedElementByNonUserInput() override;
     virtual void showImeIfNeeded() override;
 
     virtual void registerViewportLayers() const override;
 
     virtual void showUnhandledTapUIIfNeeded(IntPoint, Node*, bool) override;
+    virtual void didUpdateTopControls() const override;
 
 private:
     virtual bool isChromeClientImpl() const override { return true; }
 
     WebNavigationPolicy getNavigationPolicy(const WindowFeatures&);
     void setCursor(const WebCursorInfo&);
 
     WebViewImpl* m_webView;  // weak pointer
     WindowFeatures m_windowFeatures;
 
     PagePopupDriver* m_pagePopupDriver;
 };
 
 DEFINE_TYPE_CASTS(ChromeClientImpl, ChromeClient, client, client->isChromeClientImpl(), client.isChromeClientImpl());
 
 } // namespace blink
 
 #endif