Enable srcset support in HTMLImageElement

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 0b51791a374d39388adc0e23565c850647be29e6..304fe2f375dafaca80859672ac1c157b1e02b989 100644
--- a/Source/core/html/parser/HTMLPreloadScanner.cpp
+++ b/Source/core/html/parser/HTMLPreloadScanner.cpp
@@ -29,9 +29,11 @@
 #include "core/html/parser/HTMLPreloadScanner.h"
 
 #include "HTMLNames.h"
+#include "RuntimeEnabledFeatures.h"
 #include "core/html/InputTypeNames.h"
 #include "core/html/LinkRelAttribute.h"
 #include "core/html/parser/HTMLParserIdioms.h"
+#include "core/html/parser/HTMLSrcsetParser.h"
 #include "core/html/parser/HTMLTokenizer.h"
 #include "core/platform/chromium/TraceEvent.h"
 #include "wtf/MainThread.h"
@@ -90,10 +92,11 @@ static String initiatorFor(const StringImpl* tagImpl)
 
 class TokenPreloadScanner::StartTagScanner {
 public:
-    explicit StartTagScanner(const StringImpl* tagImpl)
+    explicit StartTagScanner(const StringImpl* tagImpl, float deviceScaleFactor)
         : m_tagImpl(tagImpl)
         , m_linkIsStyleSheet(false)
         , m_inputIsImage(false)
+        , m_deviceScaleFactor(deviceScaleFactor)
     {
         if (!match(m_tagImpl, imgTag)
             && !match(m_tagImpl, inputTag)
@@ -102,6 +105,16 @@ public:
             m_tagImpl = 0;
     }
 
+    enum URLReplacement { URLReplacementAllow, URLReplacementDisallow };

[abarth-chromium, 2013/09/13 22:24:06]

Each of these should be on its own line.

+
+

[abarth-chromium, 2013/09/13 22:24:06]

Please remove this extra blank line.

+    void applySrcset()
+    {
+        // Resolve between src and srcSet if we have them.

[abarth-chromium, 2013/09/13 22:24:06]

This "what" comment isn't needed.  Please remove it.

+        if (RuntimeEnabledFeatures::srcsetEnabled() && match(m_tagImpl, imgTag) && !m_srcSetAttribute.isEmpty())
+            setUrlToLoad(bestFitSourceForImageAttributes(m_deviceScaleFactor, m_urlToLoad, m_srcSetAttribute), URLReplacementAllow);
+    }
+
     void processAttributes(const HTMLToken::AttributeList& attributes)
     {
         ASSERT(isMainThread());
@@ -112,6 +125,8 @@ public:
             String attributeValue = StringImpl::create8BitIfPossible(iter->value);
             processAttribute(attributeName, attributeValue);
         }
+
+        applySrcset();

[abarth-chromium, 2013/09/13 22:24:06]

As I wrote before, we don't want to do any srcset specific processing for
non-img tags.  Please move this code out of the general codepath.

     }
 
     void processAttributes(const Vector<CompactHTMLToken::Attribute>& attributes)
@@ -120,6 +135,8 @@ public:
             return;
         for (Vector<CompactHTMLToken::Attribute>::const_iterator iter = attributes.begin(); iter != attributes.end(); ++iter)
             processAttribute(iter->name, iter->value);
+
+        applySrcset();
     }
 
     PassOwnPtr<PreloadRequest> createPreloadRequest(const KURL& predictedBaseURL, const SegmentedString& source)
@@ -144,19 +161,22 @@ private:
 
         if (match(m_tagImpl, scriptTag) || match(m_tagImpl, imgTag)) {
             if (match(attributeName, srcAttr))
-                setUrlToLoad(attributeValue);
+                setUrlToLoad(attributeValue, URLReplacementDisallow);

[abarth-chromium, 2013/09/13 22:24:06]

URLReplacementDisallow -> DisallowURLReplacement

Identifiers should read like normal English.

             else if (match(attributeName, crossoriginAttr) && !attributeValue.isNull())
                 m_crossOriginMode = stripLeadingAndTrailingHTMLSpaces(attributeValue);
+            else if (match(m_tagImpl, imgTag) && match(attributeName, srcsetAttr))
+                m_srcSetAttribute = attributeValue;
+
         } else if (match(m_tagImpl, linkTag)) {
             if (match(attributeName, hrefAttr))
-                setUrlToLoad(attributeValue);
+                setUrlToLoad(attributeValue, URLReplacementDisallow);
             else if (match(attributeName, relAttr))
                 m_linkIsStyleSheet = relAttributeIsStyleSheet(attributeValue);
             else if (match(attributeName, mediaAttr))
                 m_mediaAttribute = attributeValue;
         } else if (match(m_tagImpl, inputTag)) {
             if (match(attributeName, srcAttr))
-                setUrlToLoad(attributeValue);
+                setUrlToLoad(attributeValue, URLReplacementDisallow);
             else if (match(attributeName, typeAttr))
                 m_inputIsImage = equalIgnoringCase(attributeValue, InputTypeNames::image());
         }
@@ -168,13 +188,16 @@ private:
         return rel.isStyleSheet() && !rel.isAlternate() && rel.iconType() == InvalidIcon && !rel.isDNSPrefetch();
     }
 
-    void setUrlToLoad(const String& attributeValue)
+    void setUrlToLoad(const String& value, URLReplacement replacement)
     {
         // We only respect the first src/href, per HTML5:
         // http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#attribute-name-state
-        if (!m_urlToLoad.isEmpty())
+        if (replacement == URLReplacementDisallow && !m_urlToLoad.isEmpty())
+            return;
+        String url = stripLeadingAndTrailingHTMLSpaces(value);
+        if (url.isEmpty())
             return;
-        m_urlToLoad = stripLeadingAndTrailingHTMLSpaces(attributeValue);
+        m_urlToLoad = url;
     }
 
     const String& charset() const
@@ -215,16 +238,19 @@ private:
 
     const StringImpl* m_tagImpl;
     String m_urlToLoad;
+    String m_srcSetAttribute;
     String m_charset;
     String m_crossOriginMode;
     bool m_linkIsStyleSheet;
     String m_mediaAttribute;
     bool m_inputIsImage;
+    float m_deviceScaleFactor;
 };
 
-TokenPreloadScanner::TokenPreloadScanner(const KURL& documentURL)
+TokenPreloadScanner::TokenPreloadScanner(const KURL& documentURL, float deviceScaleFactor)
     : m_documentURL(documentURL)
     , m_inStyle(false)
+    , m_deviceScaleFactor(deviceScaleFactor)
     , m_templateCount(0)
 {
 }
@@ -305,7 +331,7 @@ void TokenPreloadScanner::scanCommon(const Token& token, const SegmentedString&
             return;
         }
 
-        StartTagScanner scanner(tagImpl);
+        StartTagScanner scanner(tagImpl, m_deviceScaleFactor);
         scanner.processAttributes(token.attributes());
         OwnPtr<PreloadRequest> request = scanner.createPreloadRequest(m_predictedBaseElementURL, source);
         if (request)
@@ -326,8 +352,8 @@ void TokenPreloadScanner::updatePredictedBaseURL(const Token& token)
         m_predictedBaseElementURL = KURL(m_documentURL, stripLeadingAndTrailingHTMLSpaces(hrefAttribute->value)).copy();
 }
 
-HTMLPreloadScanner::HTMLPreloadScanner(const HTMLParserOptions& options, const KURL& documentURL)
-    : m_scanner(documentURL)
+HTMLPreloadScanner::HTMLPreloadScanner(const HTMLParserOptions& options, const KURL& documentURL, float deviceScaleFactor)
+    : m_scanner(documentURL, deviceScaleFactor)
     , m_tokenizer(HTMLTokenizer::create(options))
 {
 }