Update window.devicePixelRatio on browser zoom

Source/core/page/DOMWindow.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 1227 matching lines @@
 
 double DOMWindow::devicePixelRatio() const
 {
     if (!m_frame)
         return 0.0;
 
     Page* page = m_frame->page();
     if (!page)
         return 0.0;
 
+    if (RuntimeEnabledFeatures::devicePixelRatioIncludesZoomEnabled())
+        return page->deviceScaleFactor() * m_frame->pageZoomFactor();
+
     return page->deviceScaleFactor();
 }
 
 void DOMWindow::scrollBy(int x, int y) const
 {
     if (!isCurrentlyDisplayedInFrame())
         return;
 
     document()->updateLayoutIgnorePendingStylesheets();
 
@@ skipping 467 matching lines @@
 
     Frame* child = frame->tree()->scopedChild(index);
     if (child)
         return child->domWindow();
 
     return 0;
 }
 
 
 } // namespace WebCore