Use the viewBox when scaling <svg:image>s non-uniformly w/ pAR=none

Source/core/rendering/svg/RenderSVGImage.cpp

Index: Source/core/rendering/svg/RenderSVGImage.cpp
diff --git a/Source/core/rendering/svg/RenderSVGImage.cpp b/Source/core/rendering/svg/RenderSVGImage.cpp
index 0dd6aa8942b9af18c799e3ea5363c1d2ed64cc8c..2f7849f6d695548ce67be709e40fc0cd3a1704e7 100644
--- a/Source/core/rendering/svg/RenderSVGImage.cpp
+++ b/Source/core/rendering/svg/RenderSVGImage.cpp
@@ -61,58 +61,43 @@ void RenderSVGImage::destroy()
     RenderSVGModelObject::destroy();
 }
 
-bool RenderSVGImage::forceNonUniformScaling(SVGImageElement* image) const
+FloatSize RenderSVGImage::computeImageViewportSize(ImageResource& cachedImage) const
 {
+    if (toSVGImageElement(element())->preserveAspectRatio()->currentValue()->align() != SVGPreserveAspectRatio::SVG_PRESERVEASPECTRATIO_NONE)
+        return m_objectBoundingBox.size();
+
     // Images with preserveAspectRatio=none should force non-uniform
     // scaling. This can be achieved by setting the image's container size to
-    // its intrinsic size. If the image does not have an intrinsic size - or
-    // the intrinsic size is degenerate - set the container size to the bounds
-    // as in pAR!=none cases.
+    // its viewport size (i.e. if a viewBox is available - use that - else use intrinsic size.)
     // See: http://www.w3.org/TR/SVG/single-page.html, 7.8 The ‘preserveAspectRatio’ attribute.
-    if (image->preserveAspectRatio()->currentValue()->align() != SVGPreserveAspectRatio::SVG_PRESERVEASPECTRATIO_NONE)
-        return false;
-    ImageResource* cachedImage = m_imageResource->cachedImage();
-    if (!cachedImage)
-        return false;
     Length intrinsicWidth;
     Length intrinsicHeight;
     FloatSize intrinsicRatio;
-    cachedImage->computeIntrinsicDimensions(intrinsicWidth, intrinsicHeight, intrinsicRatio);
-    if (!intrinsicWidth.isFixed() || !intrinsicHeight.isFixed())
-        return false;
-    // If the viewport defined by the referenced image is zero in either
-    // dimension, then SVGImage will have computed an intrinsic size of 300x150.
-    if (!floatValueForLength(intrinsicWidth, 0) || !floatValueForLength(intrinsicHeight, 0))
-        return false;
-    return true;
+    cachedImage.computeIntrinsicDimensions(intrinsicWidth, intrinsicHeight, intrinsicRatio);
+    return intrinsicRatio;
 }
 
 bool RenderSVGImage::updateImageViewport()
 {
     SVGImageElement* image = toSVGImageElement(element());
     FloatRect oldBoundaries = m_objectBoundingBox;
-    bool updatedViewport = false;
 
     SVGLengthContext lengthContext(image);
     m_objectBoundingBox = FloatRect(image->x()->currentValue()->value(lengthContext), image->y()->currentValue()->value(lengthContext), image->width()->currentValue()->value(lengthContext), image->height()->currentValue()->value(lengthContext));
-
     bool boundsChanged = oldBoundaries != m_objectBoundingBox;
 
-    IntSize newViewportSize;
-    if (forceNonUniformScaling(image)) {
-        LayoutSize intrinsicSize = m_imageResource->intrinsicSize(style()->effectiveZoom());
-        if (intrinsicSize != m_imageResource->imageSize(style()->effectiveZoom())) {
-            newViewportSize = roundedIntSize(intrinsicSize);
+    bool updatedViewport = false;
+    ImageResource* cachedImage = m_imageResource->cachedImage();
+    if (cachedImage && cachedImage->usesImageContainerSize()) {
+        FloatSize imageViewportSize = computeImageViewportSize(*cachedImage);
+        if (imageViewportSize != m_imageResource->imageSize(style()->effectiveZoom())) {
+            m_imageResource->setContainerSizeForRenderer(roundedIntSize(imageViewportSize));
             updatedViewport = true;
         }
-    } else if (boundsChanged) {
-        newViewportSize = enclosingIntRect(m_objectBoundingBox).size();
-        updatedViewport = true;
     }
-    if (updatedViewport)
-        m_imageResource->setContainerSizeForRenderer(newViewportSize);
+
     m_needsBoundariesUpdate |= boundsChanged;
-    return updatedViewport;
+    return updatedViewport || boundsChanged;
 }
 
 void RenderSVGImage::layout()