[SPv2] Add CSS mask support

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

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
index b2f480091b6313e4c27a4f8b5e62a73b067037f0..82ea35fea08552259baf5588f1f9bd52f1fb6d0f 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -1135,6 +1135,19 @@ void PaintLayerPainter::paintMaskForFragments(
   if (layerFragments.size() > 1)
     cacheSkipper.emplace(context);
 
+  Optional<ScopedPaintChunkProperties> scopedPaintChunkProperties;
+  if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+    const auto* objectPaintProperties =
+        m_paintLayer.layoutObject()->paintProperties();
+    DCHECK(objectPaintProperties && objectPaintProperties->maskContent());
+    PaintChunkProperties properties(
+        context.getPaintController().currentPaintChunkProperties());
+    properties.propertyTreeState.setEffect(
+        objectPaintProperties->maskContent());
+    scopedPaintChunkProperties.emplace(context.getPaintController(),
+                                       m_paintLayer, properties);
+  }
+
   for (auto& fragment : layerFragments)
     paintFragmentWithPhase(PaintPhaseMask, fragment, context,
                            fragment.backgroundRect, localPaintingInfo,