Refactor srcset parser to align it with spec changes

Source/core/html/HTMLImageElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 140 matching lines @@
         m_form->associate(*this);
     } else {
         m_form = WeakPtr<HTMLFormElement>();
     }
 }
 
 void HTMLImageElement::setBestFitURLAndDPRFromImageCandidate(const ImageCandidate& candidate)
 {
     m_bestFitImageURL = candidate.url();
     m_currentSrc = AtomicString(document().completeURL(imageSourceURL()).string());
-    float candidateScaleFactor = candidate.scaleFactor();
+    float candidateDensity = candidate.density();
     // FIXME: Make this ">0" part match the spec, once it settles.
-    if (candidateScaleFactor > 0)
-        m_imageDevicePixelRatio = 1 / candidateScaleFactor;
+    if (candidateDensity > 0)
+        m_imageDevicePixelRatio = 1 / candidateDensity;
     if (renderer() && renderer()->isImage())
         toRenderImage(renderer())->setImageDevicePixelRatio(m_imageDevicePixelRatio);
 }
 
 void HTMLImageElement::parseAttribute(const QualifiedName& name, const AtomicString& value)
 {
     if (name == altAttr) {
         if (renderer() && renderer()->isImage())
             toRenderImage(renderer())->updateAltText();
     } else if (name == srcAttr || name == srcsetAttr || name == sizesAttr) {
@@ skipping 362 matching lines @@
     if (!image)
         return FloatSize();
     LayoutSize size;
     size = image->imageSizeForRenderer(renderer(), 1.0f); // FIXME: Not sure about this.
     if (renderer() && renderer()->isRenderImage() && image->image() && !image->image()->hasRelativeWidth())
         size.scale(toRenderImage(renderer())->imageDevicePixelRatio());
     return size;
 }
 
 }