Bug 608812 - Should snap subpixel value for outer svg and anon child r=longsonr

We should  snap subpixel value at nsDisplayTransform::GetResultingTransformMatrix
for outer svg and the anon child. This will solve blurry rendering for subpixel position
when webrender is __not__ enabled.

Differential Revision: https://phabricator.services.mozilla.com/D29344

--HG--
extra : moz-landing-system : lando

layout/painting/nsDisplayList.cpp

@@ -7803,10 +7803,15 @@ Matrix4x4 nsDisplayTransform::GetResultingTransformMatrixInternal(
       frame &&
       frame->IsSVGTransformed(&svgTransform, &parentsChildrenOnlyTransform);
 
+  bool shouldRound = true;
+
   // An SVG frame should not have its translation rounded.
   // Note it's possible that the SVG frame doesn't have an SVG
   // transform but only has a CSS transform.
-  bool shouldRound = !(frame && frame->IsFrameOfType(nsIFrame::eSVG));
+  if (frame && frame->HasAnyStateBits(NS_FRAME_SVG_LAYOUT) &&
+      !frame->IsSVGOuterSVGAnonChildFrame()) {
+    shouldRound = false;
+  }
 
   /* Transformed frames always have a transform, or are preserving 3d (and might
    * still have perspective!) */

layout/reftests/w3c-css/submitted/images3/reftest.list

@@ -181,13 +181,13 @@ fails-if(!webrender) == object-position-png-002c.html object-position-png-002-re
 == object-position-png-002i.html object-position-png-002-ref.html
 == object-position-png-002o.html object-position-png-002-ref.html
 == object-position-png-002p.html object-position-png-002-ref.html
-fails-if(!webrender) random-if(webrender) == object-position-svg-001e.html object-position-svg-001-ref.html # bug 1103286
+random-if(webrender) == object-position-svg-001e.html object-position-svg-001-ref.html # bug 1103286
 == object-position-svg-001i.html object-position-svg-001-ref.html
-fails-if(!webrender) random-if(webrender) == object-position-svg-001o.html object-position-svg-001-ref.html # bug 1103286
+random-if(webrender) == object-position-svg-001o.html object-position-svg-001-ref.html # bug 1103286
 == object-position-svg-001p.html object-position-svg-001-ref.html
-fails == object-position-svg-002e.html object-position-svg-002-ref.html # bug 1103286
+fails-if(webrender) == object-position-svg-002e.html object-position-svg-002-ref.html # bug 1103286
 == object-position-svg-002i.html object-position-svg-002-ref.html
-fails == object-position-svg-002o.html object-position-svg-002-ref.html # bug 1103286
+fails-if(webrender) == object-position-svg-002o.html object-position-svg-002-ref.html # bug 1103286
 == object-position-svg-002p.html object-position-svg-002-ref.html
 
 # Tests for gradient color stops with 'currentcolor'