Have srcset respond to viewport changes

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 ceeb1ede0923b0b2912ddc8e3cd7f60df49ccb64..9543bd3f4b1d8a6c3d0836a35bbcb1a62a2d81f7 100644
--- a/Source/core/html/HTMLImageElement.cpp
+++ b/Source/core/html/HTMLImageElement.cpp
@@ -54,6 +54,9 @@ HTMLImageElement::HTMLImageElement(Document& document, HTMLFormElement* form, bo
     , m_imageDevicePixelRatio(1.0f)
     , m_formWasSetByParser(false)
     , m_elementCreatedByParser(createdByParser)
+    , m_intrinsicSizingViewportDependant(false)
+    , m_effectiveSizeViewportDependant(false)
+    , m_viewportListener(ImageViewportChangeListener::create(this))
 {
     ScriptWrappable::init(this);
     if (form && form->inDocument()) {
@@ -81,6 +84,7 @@ PassRefPtrWillBeRawPtr<HTMLImageElement> HTMLImageElement::create(Document& docu
 HTMLImageElement::~HTMLImageElement()
 {
 #if !ENABLE(OILPAN)
+    document().viewportChangeNotifier().removeListener(m_viewportListener.get());

[esprehn, 2014/07/14 08:39:49]

Or slower...

     if (m_form)
         m_form->disassociate(*this);
 #endif
@@ -181,6 +185,8 @@ void HTMLImageElement::setBestFitURLAndDPRFromImageCandidate(const ImageCandidat
     float candidateDensity = candidate.density();
     if (candidateDensity >= 0)
         m_imageDevicePixelRatio = 1.0 / candidateDensity;
+    if (candidate.resourceWidth() > 0)
+        m_intrinsicSizingViewportDependant = true;
     if (renderer() && renderer()->isImage())
         toRenderImage(renderer())->setImageDevicePixelRatio(m_imageDevicePixelRatio);
 }
@@ -246,7 +252,7 @@ ImageCandidate HTMLImageElement::findBestFitImageFromPictureParent()
         if (!source->mediaQueryMatches())
             continue;
 
-        unsigned effectiveSize = SizesAttributeParser::findEffectiveSize(source->fastGetAttribute(sizesAttr), MediaValuesDynamic::create(document()));
+        unsigned effectiveSize = SizesAttributeParser::findEffectiveSize(source->fastGetAttribute(sizesAttr), MediaValuesDynamic::create(document()), m_effectiveSizeViewportDependant);
         ImageCandidate candidate = bestFitSourceForSrcsetAttribute(document().devicePixelRatio(), effectiveSize, source->fastGetAttribute(srcsetAttr));
         if (candidate.isEmpty())
             continue;
@@ -569,10 +575,12 @@ void HTMLImageElement::selectSourceURL(ImageLoader::UpdateFromElementBehavior be
     if (!foundURL) {
         unsigned effectiveSize = 0;
         if (RuntimeEnabledFeatures::pictureSizesEnabled())
-            effectiveSize = SizesAttributeParser::findEffectiveSize(fastGetAttribute(sizesAttr), MediaValuesDynamic::create(document()));
+            effectiveSize = SizesAttributeParser::findEffectiveSize(fastGetAttribute(sizesAttr), MediaValuesDynamic::create(document()), m_effectiveSizeViewportDependant);
         ImageCandidate candidate = bestFitSourceForImageAttributes(document().devicePixelRatio(), effectiveSize, fastGetAttribute(srcAttr), fastGetAttribute(srcsetAttr));
         setBestFitURLAndDPRFromImageCandidate(candidate);
     }
+    if (m_intrinsicSizingViewportDependant && m_effectiveSizeViewportDependant)
+        document().viewportChangeNotifier().addListener(m_viewportListener.get());
     imageLoader().updateFromElement(behavior);
 }