Add preloader support for picture based source selection

Source/core/html/parser/HTMLPreloadScanner.cpp

Index: Source/core/html/parser/HTMLPreloadScanner.cpp
diff --git a/Source/core/html/parser/HTMLPreloadScanner.cpp b/Source/core/html/parser/HTMLPreloadScanner.cpp
index 706fb0e51034b954e74e60534ba1610ac8e53691..fa0fdaa2bde027d2d7840cad123862735cfd5f31 100644
--- a/Source/core/html/parser/HTMLPreloadScanner.cpp
+++ b/Source/core/html/parser/HTMLPreloadScanner.cpp
@@ -108,19 +108,22 @@ public:
         , m_linkIsStyleSheet(false)
         , m_matchedMediaAttribute(true)
         , m_inputIsImage(false)
-        , m_imgSourceSize(0)
+        , m_sourceSize(0)
         , m_sourceSizeSet(false)
         , m_isCORSEnabled(false)
         , m_allowCredentials(DoNotAllowStoredCredentials)
         , m_mediaValues(mediaValues)
     {
-        if (!match(m_tagImpl, imgTag)
-            && !match(m_tagImpl, inputTag)
+        if (match(m_tagImpl, imgTag)
+            || match(m_tagImpl, sourceTag)) {
+            if (RuntimeEnabledFeatures::pictureSizesEnabled())
+                m_sourceSize = SizesAttributeParser::findEffectiveSize(String(), m_mediaValues);
+            return;
+        }
+        if ( !match(m_tagImpl, inputTag)
             && !match(m_tagImpl, linkTag)
             && !match(m_tagImpl, scriptTag))
             m_tagImpl = 0;
-        if (RuntimeEnabledFeatures::pictureSizesEnabled())
-            m_imgSourceSize = SizesAttributeParser::findEffectiveSize(String(), m_mediaValues);
     }
 
     enum URLReplacement {
@@ -148,6 +151,18 @@ public:
             processAttribute(iter->name, iter->value);
     }
 
+    void handlePictureSourceURL(Vector<Parent>& pictureParentStack)
+    {
+        if (pictureParentStack.isEmpty() || !match(pictureParentStack.last().tagImpl, pictureTag))
+            return;
+
+        Parent& parent = pictureParentStack.last();
+        if (match(m_tagImpl, sourceTag) && m_matchedMediaAttribute && parent.sourceURL.isEmpty())
+            parent.sourceURL = m_srcsetImageCandidate.toString();
+        else if (match(m_tagImpl, imgTag) && !parent.sourceURL.isEmpty())
+            setUrlToLoad(parent.sourceURL, AllowURLReplacement);
+    }
+
     PassOwnPtr<PreloadRequest> createPreloadRequest(const KURL& predictedBaseURL, const SegmentedString& source)
     {
         if (!shouldPreload() || !m_matchedMediaAttribute)
@@ -164,49 +179,98 @@ public:
 
 private:
     template<typename NameType>
+    void processScriptAttribute(const NameType& attributeName, const String& attributeValue)
+    {
+        // FIXME - What should happen if we have multiple crossOrigin attributes with different values?
+        if (match(attributeName, srcAttr))
+            setUrlToLoad(attributeValue, DisallowURLReplacement);
+        else if (match(attributeName, crossoriginAttr))
+            setCrossOriginAllowed(attributeValue);
+    }
+
+    template<typename NameType>
+    void processImgAttribute(const NameType& attributeName, const String& attributeValue)
+    {
+        if (match(attributeName, srcAttr) && m_imgSrcUrl.isNull()) {
+            m_imgSrcUrl = attributeValue;
+            setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_sourceSize, attributeValue, m_srcsetImageCandidate), AllowURLReplacement);
+        } else if (match(attributeName, crossoriginAttr)) {
+            setCrossOriginAllowed(attributeValue);
+        } else if (match(attributeName, srcsetAttr) && m_srcsetImageCandidate.isEmpty()) {
+            m_srcsetAttributeValue = attributeValue;
+            m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), m_sourceSize, attributeValue);
+            setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_sourceSize, m_imgSrcUrl, m_srcsetImageCandidate), AllowURLReplacement);
+        } else if (RuntimeEnabledFeatures::pictureSizesEnabled() && match(attributeName, sizesAttr) && !m_sourceSizeSet) {
+            m_sourceSize = SizesAttributeParser::findEffectiveSize(attributeValue, m_mediaValues);
+            m_sourceSizeSet = true;
+            if (!m_srcsetImageCandidate.isEmpty()) {
+                m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), m_sourceSize, m_srcsetAttributeValue);
+                setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_sourceSize, m_imgSrcUrl, m_srcsetImageCandidate), AllowURLReplacement);
+            }
+        }
+    }
+
+    template<typename NameType>
+    void processLinkAttribute(const NameType& attributeName, const String& attributeValue)
+    {
+        // FIXME - What should happen if we have multiple rel/media/crossOrigin attributes of the same name, with different values?
+        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);
+    }
+
+    template<typename NameType>
+    void processInputAttribute(const NameType& attributeName, const String& attributeValue)
+    {
+        // FIXME - What should happen if we have multiple type attributes with different values?
+        if (match(attributeName, srcAttr))
+            setUrlToLoad(attributeValue, DisallowURLReplacement);
+        else if (match(attributeName, typeAttr))
+            m_inputIsImage = equalIgnoringCase(attributeValue, InputTypeNames::image);
+    }
+
+    template<typename NameType>
+    void processSourceAttribute(const NameType& attributeName, const String& attributeValue)
+    {
+        if (!RuntimeEnabledFeatures::pictureEnabled())
+            return;
+        if (match(attributeName, srcsetAttr) && m_srcsetImageCandidate.isEmpty()) {
+            m_srcsetAttributeValue = attributeValue;
+            m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), m_sourceSize, attributeValue);
+        } else if (match(attributeName, sizesAttr) && !m_sourceSizeSet) {
+            m_sourceSize = SizesAttributeParser::findEffectiveSize(attributeValue, m_mediaValues);
+            m_sourceSizeSet = true;
+            if (!m_srcsetImageCandidate.isEmpty()) {
+                m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), m_sourceSize, m_srcsetAttributeValue);
+            }
+        } else if (match(attributeName, mediaAttr)) {
+            // FIXME - What should happen if we have multiple media attributes???
+            m_matchedMediaAttribute = mediaAttributeMatches(*m_mediaValues, attributeValue);
+        }
+
+    }
+
+    template<typename NameType>
     void processAttribute(const NameType& attributeName, const String& attributeValue)
     {
         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)) {
-            if (match(attributeName, srcAttr) && m_imgSrcUrl.isNull()) {
-                m_imgSrcUrl = attributeValue;
-                setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_imgSourceSize, attributeValue, m_srcsetImageCandidate), AllowURLReplacement);
-            } else if (match(attributeName, crossoriginAttr)) {
-                setCrossOriginAllowed(attributeValue);
-            } else if (match(attributeName, srcsetAttr) && m_srcsetImageCandidate.isEmpty()) {
-                m_imgSrcsetAttributeValue = attributeValue;
-                m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), m_imgSourceSize, attributeValue);
-                setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_imgSourceSize, m_imgSrcUrl, m_srcsetImageCandidate), AllowURLReplacement);
-            } else if (RuntimeEnabledFeatures::pictureSizesEnabled() && match(attributeName, sizesAttr) && !m_sourceSizeSet) {
-                m_imgSourceSize = SizesAttributeParser::findEffectiveSize(attributeValue, m_mediaValues);
-                m_sourceSizeSet = true;
-                if (!m_srcsetImageCandidate.isEmpty()) {
-                    m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), m_imgSourceSize, m_imgSrcsetAttributeValue);
-                    setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_imgSourceSize, m_imgSrcUrl, 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);
-        } else if (match(m_tagImpl, inputTag)) {
-            if (match(attributeName, srcAttr))
-                setUrlToLoad(attributeValue, DisallowURLReplacement);
-            else if (match(attributeName, typeAttr))
-                m_inputIsImage = equalIgnoringCase(attributeValue, InputTypeNames::image);
-        }
+        if (match(m_tagImpl, scriptTag))
+            processScriptAttribute(attributeName, attributeValue);
+        else if (match(m_tagImpl, imgTag))
+            processImgAttribute(attributeName, attributeValue);
+        else if (match(m_tagImpl, linkTag))
+            processLinkAttribute(attributeName, attributeValue);
+        else if (match(m_tagImpl, inputTag))
+            processInputAttribute(attributeName, attributeValue);
+        else if (match(m_tagImpl, sourceTag))
+            processSourceAttribute(attributeName, attributeValue);
     }
 
     static bool relAttributeIsStyleSheet(const String& attributeValue)
@@ -285,8 +349,8 @@ private:
     bool m_matchedMediaAttribute;
     bool m_inputIsImage;
     String m_imgSrcUrl;
-    String m_imgSrcsetAttributeValue;
-    unsigned m_imgSourceSize;
+    String m_srcsetAttributeValue;
+    unsigned m_sourceSize;
     bool m_sourceSizeSet;
     bool m_isCORSEnabled;
     StoredCredentials m_allowCredentials;
@@ -333,6 +397,26 @@ void TokenPreloadScanner::scan(const CompactHTMLToken& token, const SegmentedStr
     scanCommon(token, source, requests);
 }
 
+static bool startNesting(const StringImpl* tagImpl, bool selfClosing)
+{
+    if (selfClosing
+        || match(tagImpl, sourceTag)
+        || match(tagImpl, imgTag)
+        || match(tagImpl, areaTag)
+        || match(tagImpl, baseTag)
+        || match(tagImpl, brTag)
+        || match(tagImpl, colTag)
+        || match(tagImpl, hrTag)
+        || match(tagImpl, inputTag)
+        || match(tagImpl, linkTag)
+        || match(tagImpl, metaTag)
+        || match(tagImpl, paramTag)
+        || match(tagImpl, commandTag)
+        || match(tagImpl, keygenTag))
+        return false;
+    return true;
+}
+
 template<typename Token>
 void TokenPreloadScanner::scanCommon(const Token& token, const SegmentedString& source, PreloadRequestStream& requests)
 {
@@ -350,6 +434,8 @@ void TokenPreloadScanner::scanCommon(const Token& token, const SegmentedString&
                 --m_templateCount;
             return;
         }
+        if (!m_pictureParentStack.isEmpty() && startNesting(tagImpl, token.selfClosing()) && m_pictureParentStack.last().tagImpl == tagImpl)
+            m_pictureParentStack.removeLast();
         if (match(tagImpl, styleTag)) {
             if (m_inStyle)
                 m_cssScanner.reset();
@@ -361,6 +447,10 @@ void TokenPreloadScanner::scanCommon(const Token& token, const SegmentedString&
         if (m_templateCount)
             return;
         const StringImpl* tagImpl = tagImplFor(token.data());
+        if (RuntimeEnabledFeatures::pictureEnabled()
+            && ((match(tagImpl, pictureTag)) || (!m_pictureParentStack.isEmpty() && startNesting(tagImpl, token.selfClosing())))) {
+            m_pictureParentStack.append(Parent(tagImpl));
+        }
         if (match(tagImpl, templateTag)) {
             ++m_templateCount;
             return;
@@ -379,6 +469,7 @@ void TokenPreloadScanner::scanCommon(const Token& token, const SegmentedString&
 
         StartTagScanner scanner(tagImpl, m_mediaValues);
         scanner.processAttributes(token.attributes());
+        scanner.handlePictureSourceURL(m_pictureParentStack);
         OwnPtr<PreloadRequest> request = scanner.createPreloadRequest(m_predictedBaseElementURL, source);
         if (request)
             requests.append(request.release());