Adds DevTools commands for forced viewport override.

third_party/WebKit/Source/core/page/ChromeClient.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple, Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 151 matching lines @@
     virtual WebScreenInfo screenInfo() const = 0;
     virtual void setCursor(const Cursor&, LocalFrame* localRoot) = 0;
     // End methods used by HostWindow.
     virtual Cursor lastSetCursorForTesting() const = 0;
 
     virtual void dispatchViewportPropertiesDidChange(const ViewportDescription&) const { }
 
     virtual void contentsSizeChanged(LocalFrame*, const IntSize&) const = 0;
     virtual void pageScaleFactorChanged() const { }
     virtual float clampPageScaleFactorToLimits(float scale) const { return scale; }
+    virtual void mainFrameScrollOffsetChanged() const {}
     virtual void layoutUpdated(LocalFrame*) const { }
 
     void mouseDidMoveOverElement(const HitTestResult&);
     virtual void setToolTip(const String&, TextDirection) = 0;
     void clearToolTip();
 
     void print(LocalFrame*);
 
     virtual void annotatedRegionsChanged() = 0;
 
@@ skipping 119 matching lines @@
 
     LayoutPoint m_lastToolTipPoint;
     String m_lastToolTipText;
 
     FRIEND_TEST_ALL_PREFIXES(ChromeClientTest, SetToolTipFlood);
 };
 
 } // namespace blink
 
 #endif // ChromeClient_h