Extend srcset's syntax to include 'w' descriptors

Source/core/html/parser/HTMLPreloadScanner.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009 Torch Mobile, Inc. http://www.torchmobile.com/
  * Copyright (C) 2010 Google Inc. All Rights Reserved.
  *
  * 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.
@@ skipping 153 matching lines @@
     {
         if (match(attributeName, charsetAttr))
             m_charset = attributeValue;
 
         if (match(m_tagImpl, scriptTag)) {
             if (match(attributeName, srcAttr))
                 setUrlToLoad(attributeValue, DisallowURLReplacement);
             else if (match(attributeName, crossoriginAttr))
                 setCrossOriginAllowed(attributeValue);
         } else if (match(m_tagImpl, imgTag)) {
+            int effectiveSize = -1; // FIXME - hook up the real value from `sizes`
             if (match(attributeName, srcAttr) && !m_encounteredImgSrc) {
                 m_encounteredImgSrc = true;
-                setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), attributeValue, m_srcsetImageCandidate), AllowURLReplacement);
+                setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), effectiveSize, attributeValue, m_srcsetImageCandidate), AllowURLReplacement);
             } else if (match(attributeName, crossoriginAttr)) {
                 setCrossOriginAllowed(attributeValue);
             } else if (RuntimeEnabledFeatures::srcsetEnabled()
                 && match(attributeName, srcsetAttr)
                 && m_srcsetImageCandidate.isEmpty()) {
-                m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), attributeValue);
-                setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_urlToLoad, m_srcsetImageCandidate), AllowURLReplacement);
+                m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), effectiveSize, attributeValue);
+                setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), effectiveSize, m_urlToLoad, m_srcsetImageCandidate), AllowURLReplacement);
             }
         } else if (match(m_tagImpl, linkTag)) {
             if (match(attributeName, hrefAttr))
                 setUrlToLoad(attributeValue, DisallowURLReplacement);
             else if (match(attributeName, relAttr))
                 m_linkIsStyleSheet = relAttributeIsStyleSheet(attributeValue);
             else if (match(attributeName, mediaAttr))
                 m_matchedMediaAttribute = mediaAttributeMatches(*m_mediaValues, attributeValue);
             else if (match(attributeName, crossoriginAttr))
                 setCrossOriginAllowed(attributeValue);
@@ skipping 222 matching lines @@
         if (m_token.type() == HTMLToken::StartTag)
             m_tokenizer->updateStateFor(attemptStaticStringCreation(m_token.name(), Likely8Bit));
         m_scanner.scan(m_token, m_source, requests);
         m_token.clear();
     }
 
     preloader->takeAndPreload(requests);
 }
 
 }