Use srcset's resource pixel density to determine intrinsic size

Source/core/rendering/RenderImage.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2006 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010, 2011 Apple Inc. 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
@@ skipping 43 matching lines @@
     void areaElementFocusChanged(HTMLAreaElement*);
 
     void highQualityRepaintTimerFired(Timer<RenderImage>*);
 
     void setIsGeneratedContent(bool generated = true) { m_isGeneratedContent = generated; }
 
     bool isGeneratedContent() const { return m_isGeneratedContent; }
 
     String altText() const { return m_altText; }
 
+    inline void setImageDevicePixelRatio(float factor) { m_imageDevicePixelRatio = factor; }
+    float imageDevicePixelRatio() const { return m_imageDevicePixelRatio; }
+
 protected:
     virtual bool needsPreferredWidthsRecalculation() const OVERRIDE FINAL;
     virtual RenderBox* embeddedContentBox() const OVERRIDE FINAL;
     virtual void computeIntrinsicRatioInformation(FloatSize& intrinsicSize, double& intrinsicRatio, bool& isPercentageIntrinsicSize) const OVERRIDE FINAL;
 
     virtual void styleDidChange(StyleDifference, const RenderStyle*) OVERRIDE FINAL;
 
     virtual void imageChanged(WrappedImagePtr, const IntRect* = 0);
 
     void paintIntoRect(GraphicsContext*, const LayoutRect&);
@@ skipping 31 matching lines @@
     void updateInnerContentRect();
 
     void paintAreaElementFocusRing(PaintInfo&);
 
     // Text to display as long as the image isn't available.
     String m_altText;
     OwnPtr<RenderImageResource> m_imageResource;
     bool m_needsToSetSizeForAltText;
     bool m_didIncrementVisuallyNonEmptyPixelCount;
     bool m_isGeneratedContent;
+    float m_imageDevicePixelRatio;
 
     friend class RenderImageScaleObserver;
 };
 
 inline RenderImage* toRenderImage(RenderObject* object)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderImage());
     return static_cast<RenderImage*>(object);
 }
 
 inline const RenderImage* toRenderImage(const RenderObject* object)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderImage());
     return static_cast<const RenderImage*>(object);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toRenderImage(const RenderImage*);
 
 } // namespace WebCore
 
 #endif // RenderImage_h