[SPv2] Add CSS mask support

third_party/WebKit/Source/core/paint/PaintLayer.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index 77b9cddafecb866ce990f62ccc2089e1fa3b3102..3bc9fb9d94a58b56fb0d5e0dcc327fd010aac0b5 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -2675,6 +2675,9 @@ void PaintLayer::setGroupedMapping(CompositedLayerMapping* groupedMapping,
 }
 
 bool PaintLayer::hasCompositedMask() const {

[trchen, 2017/01/21 01:27:08]

Is it obvious to you why this change is needed? I feel this function could use
some good comments.

[chrishtr, 2017/01/24 01:16:28]

Maybe just rename the method to something like
applyBlendToMaskOutputWhenPainting?
It's pretty obvious what the two callsites are doing to anyone who needs to
know.

[trchen, 2017/02/11 02:35:45]

"maskBlendingAppliedByCompositor" to avoid negation. Also code reads better in
my totally subject opinion. :D

+  DCHECK(m_layoutObject->hasMask());
+  if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
+    return true;
   return m_rareData && m_rareData->compositedLayerMapping &&
          m_rareData->compositedLayerMapping->hasMaskLayer();
 }