Align srcset parsing with spec changes

Source/core/html/parser/HTMLSrcsetParser.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 57 matching lines @@
         if (*currentDescriptorEnd == 'x') {
             if (result.foundDescriptor())
                 return false;
             result.scaleFactor = charactersToFloat(currentDescriptorStart, descriptorLength, &isValid);
             if (!isValid || result.scaleFactor < 0)
                 return false;
         } else if (RuntimeEnabledFeatures::pictureSizesEnabled() && *currentDescriptorEnd == 'w') {
             if (result.foundDescriptor())
                 return false;
             result.resourceWidth = charactersToInt(currentDescriptorStart, descriptorLength, &isValid);
-            if (!isValid || result.resourceWidth < 0)
+            if (!isValid || result.resourceWidth <= 0)
                 return false;
         }
     }
     if (isEmptyDescriptor)
         result.scaleFactor = 1.0;
     return result.foundDescriptor();
 }
 
 // http://www.whatwg.org/specs/web-apps/current-work/multipage/embedded-content-1.html#processing-the-image-candidates
 template<typename CharType>
@@ skipping 26 matching lines @@
         } else {
             // 7. Collect a sequence of characters that are not "," (U+002C) characters, and let that be descriptors.
             skipWhile<CharType, isHTMLSpace<CharType> >(position, attributeEnd);
             const CharType* descriptorsStart = position;
             skipUntil<CharType, isComma<CharType> >(position, attributeEnd);
             const CharType* descriptorsEnd = position;
             if (!parseDescriptors(descriptorsStart, descriptorsEnd, result))
                 continue;
         }
 
-        imageCandidates.append(ImageCandidate(attribute, imageURLStart - attributeStart, imageURLEnd - imageURLStart, result));
+        ASSERT(imageURLEnd > attributeStart);
+        unsigned imageURLStartingPosition = imageURLStart - attributeStart;
+        ASSERT(imageURLEnd > imageURLStart);
+        unsigned imageURLLength = imageURLEnd - imageURLStart;
+        imageCandidates.append(ImageCandidate(attribute, imageURLStartingPosition, imageURLLength, result, ImageCandidate::SrcsetOrigin));
         // 11. Return to the step labeled splitting loop.
     }
 }
 
 static void parseImageCandidatesFromSrcsetAttribute(const String& attribute, Vector<ImageCandidate>& imageCandidates)
 {
     if (attribute.isNull())
         return;
 
     if (attribute.is8Bit())
         parseImageCandidatesFromSrcsetAttribute<LChar>(attribute, attribute.characters8(), attribute.length(), imageCandidates);
     else
         parseImageCandidatesFromSrcsetAttribute<UChar>(attribute, attribute.characters16(), attribute.length(), imageCandidates);
 }
 
 static ImageCandidate pickBestImageCandidate(float deviceScaleFactor, int effectiveSize, Vector<ImageCandidate>& imageCandidates)
 {
+    bool ignoreSrc = false;
     if (imageCandidates.isEmpty())
         return ImageCandidate();
 
     // http://picture.responsiveimages.org/#normalize-source-densities
     for (Vector<ImageCandidate>::iterator it = imageCandidates.begin(); it != imageCandidates.end(); ++it) {
-        if (it->scaleFactor() < 0)
+        if (it->resourceWidth() > 0) {
             it->setScaleFactor((float)it->resourceWidth() / (float)effectiveSize);
+            ignoreSrc = true;
+        }
     }
 
     std::stable_sort(imageCandidates.begin(), imageCandidates.end(), compareByScaleFactor);
 
     unsigned i;
     for (i = 0; i < imageCandidates.size() - 1; ++i) {
-        if (imageCandidates[i].scaleFactor() >= deviceScaleFactor)
+        if ((imageCandidates[i].scaleFactor() >= deviceScaleFactor) && (!ignoreSrc || !imageCandidates[i].srcOrigin()))
             break;
     }
 
     float winningScaleFactor = imageCandidates[i].scaleFactor();
     unsigned winner = i;
     // 16. If an entry b in candidates has the same associated ... pixel density as an earlier entry a in candidates,
     // then remove entry b
     while ((i > 0) && (imageCandidates[--i].scaleFactor() == winningScaleFactor))
         winner = i;
 
@@ skipping 10 matching lines @@
 }
 
 ImageCandidate bestFitSourceForImageAttributes(float deviceScaleFactor, int effectiveSize, const String& srcAttribute, const String& srcsetAttribute)
 {
     DescriptorParsingResult defaultResult;
     defaultResult.scaleFactor = 1.0;
 
     if (srcsetAttribute.isNull()) {
         if (srcAttribute.isNull())
             return ImageCandidate();
-        return ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult);
+        return ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult, ImageCandidate::SrcOrigin);
     }
 
     Vector<ImageCandidate> imageCandidates;
 
     parseImageCandidatesFromSrcsetAttribute(srcsetAttribute, imageCandidates);
 
     if (!srcAttribute.isEmpty())
-        imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult));
+        imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult, ImageCandidate::SrcOrigin));
 
     return pickBestImageCandidate(deviceScaleFactor, effectiveSize, imageCandidates);
 }
 
 String bestFitSourceForImageAttributes(float deviceScaleFactor, int effectiveSize, const String& srcAttribute, ImageCandidate& srcsetImageCandidate)
 {
     DescriptorParsingResult defaultResult;
     defaultResult.scaleFactor = 1.0;
 
     if (srcsetImageCandidate.isEmpty())
         return srcAttribute;
 
     Vector<ImageCandidate> imageCandidates;
     imageCandidates.append(srcsetImageCandidate);
 
     if (!srcAttribute.isEmpty())
-        imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult));
+        imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult, ImageCandidate::SrcOrigin));
 
     return pickBestImageCandidate(deviceScaleFactor, effectiveSize, imageCandidates).toString();
 }
 
 }