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 162 matching lines @@
 #else
         m_form = WeakPtr<HTMLFormElement>();
 #endif
     }
 }
 
 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 380 matching lines @@
             effectiveSize = SizesAttributeParser::findEffectiveSize(fastGetAttribute(sizesAttr), MediaValuesCached::create(document()));
         ImageCandidate candidate = bestFitSourceForImageAttributes(document().devicePixelRatio(), effectiveSize, fastGetAttribute(srcAttr), fastGetAttribute(srcsetAttr));
         setBestFitURLAndDPRFromImageCandidate(candidate);
     }
     if (behavior == UpdateIgnorePreviousError)
         m_imageLoader.updateFromElementIgnoringPreviousError();
     else
         m_imageLoader.updateFromElement();
 }
 }