Use srcset's resource pixel density to determine intrinsic size

Source/core/rendering/RenderImage.h

Index: Source/core/rendering/RenderImage.h
diff --git a/Source/core/rendering/RenderImage.h b/Source/core/rendering/RenderImage.h
index 1204ea5ed79bd0ae5b6fd0ff4acbe8d51cfbfb96..3fceb431e9ac58555f553a038b7482f97abdbbaa 100644
--- a/Source/core/rendering/RenderImage.h
+++ b/Source/core/rendering/RenderImage.h
@@ -61,6 +61,9 @@ public:
 
     String altText() const { return m_altText; }
 
+    inline void setIntrinsicSizeFactor(float factor) { m_intrinsicSizeFactor = factor; }
+    virtual LayoutSize intrinsicSize() const OVERRIDE;
+    LayoutSize unscaledIntrinsicSize() const;

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

Can we change this to something more descriptive? Possibly
"intrinsicSizeWithoutSrcsetDevicePixelRatio()"?
Similarly for the intrinsicSizeFactor. Possibly "m_srcsetDevicePixelRatio" and
"setSrcsetDevicePixelRatio(...)"?
Similarly for HTMLImageElement, etc.

This sounds pedantic but there are already several scale factors (ctm scale,
screen's device pixel ratio, page zoom scale) and it sounds like we're even
going to add another device pixel ratio soon (for client hints).

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

I think (hope) this mechanism is not srcset specific, and CH, image-set and srcN
could use it just as well.

Maybe intrinsicSizeWithoutDevicePixelRatio() ?

 protected:
     virtual bool needsPreferredWidthsRecalculation() const OVERRIDE FINAL;
     virtual RenderBox* embeddedContentBox() const OVERRIDE FINAL;
@@ -101,6 +104,7 @@ private:
     IntSize imageSizeForError(ImageResource*) const;
     void imageDimensionsChanged(bool imageSizeChanged, const IntRect* = 0);
     bool updateIntrinsicSizeIfNeeded(const LayoutSize&, bool imageSizeChanged);
+    virtual float intrinsicSizeFactor() const { return m_intrinsicSizeFactor; }
     // Update the size of the image to be rendered. Object-fit may cause this to be different from the CSS box's content rect.
     void updateInnerContentRect();
 
@@ -112,6 +116,7 @@ private:
     bool m_needsToSetSizeForAltText;
     bool m_didIncrementVisuallyNonEmptyPixelCount;
     bool m_isGeneratedContent;
+    float m_intrinsicSizeFactor;
 
     friend class RenderImageScaleObserver;
 };