Use srcset's resource pixel density to determine intrinsic size

Source/core/html/HTMLImageElement.cpp

Index: Source/core/html/HTMLImageElement.cpp
diff --git a/Source/core/html/HTMLImageElement.cpp b/Source/core/html/HTMLImageElement.cpp
index 68ee58fc2406e89426fba1bc9b8d5fbf1be0dece..b6d7772dcefd884f171aa026dc9797e91109b43a 100644
--- a/Source/core/html/HTMLImageElement.cpp
+++ b/Source/core/html/HTMLImageElement.cpp
@@ -47,6 +47,7 @@ HTMLImageElement::HTMLImageElement(const QualifiedName& tagName, Document& docum
     , m_imageLoader(this)
     , m_form(form)
     , m_compositeOperator(CompositeSourceOver)
+    , m_intrinsicSizeFactor(1.0f)
 {
     ASSERT(hasTagName(imgTag));
     ScriptWrappable::init(this);
@@ -121,7 +122,7 @@ void HTMLImageElement::parseAttribute(const QualifiedName& name, const AtomicStr
             toRenderImage(renderer())->updateAltText();
     } else if (name == srcAttr || name == srcsetAttr) {
         if (RuntimeEnabledFeatures::srcsetEnabled())
-            m_bestFitImageURL = bestFitSourceForImageAttributes(document().devicePixelRatio(), fastGetAttribute(srcAttr), fastGetAttribute(srcsetAttr));
+            m_bestFitImageURL = bestFitSourceForImageAttributes(document().devicePixelRatio(), fastGetAttribute(srcAttr), fastGetAttribute(srcsetAttr), m_intrinsicSizeFactor);
         m_imageLoader.updateFromElementIgnoringPreviousError();
     }
     else if (name == usemapAttr)
@@ -156,6 +157,7 @@ RenderObject* HTMLImageElement::createRenderer(RenderStyle* style)
 
     RenderImage* image = new RenderImage(this);
     image->setImageResource(RenderImageResource::create());
+    image->setIntrinsicSizeFactor(m_intrinsicSizeFactor);

[pdr., 2013/10/11 05:17:33]

I'm not sure this will work for dynamic changes. For example:
<img srcset="mustard.png 2x">
<script>
document.body.onload = function() {
  var img = document.getElementsByTagName('img')[0];
  img.srcset = "ketchup.png 3x";
}
</script>

In this example, we wont create a new RenderImage but m_intrinsicSizeFactor will
change. One solution may be to set the value in parseAttribute if there's
already a renderer, similar to how the alt text is updated.

[Yoav Weiss, 2013/10/11 07:22:32]

Good catch! Will fix.

     return image;
 }