Let page zoom affect resolution and -webkit-device-pixel-ratio MQs.

Source/core/page/Frame.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 691 matching lines @@
         return nullptr;
     buffer->context()->translate(-paintingRect.x(), -paintingRect.y());
     buffer->context()->clip(FloatRect(0, 0, paintingRect.maxX(), paintingRect.maxY()));
 
     m_view->paintContents(buffer->context(), paintingRect);
 
     RefPtr<Image> image = buffer->copyImage();
     return DragImage::create(image.get());
 }
 
+double Frame::devicePixelRatio() const
+{
+    if (!m_page)
+        return 0;
+
+    double ratio = m_page->deviceScaleFactor();
+    if (RuntimeEnabledFeatures::devicePixelRatioIncludesZoomEnabled())
+        ratio *= pageZoomFactor();
+    return ratio;
+}
+
 } // namespace WebCore