Apply CSS clip to foreground and background clip rects.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp b/third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp
index e7dbd7470e30caf86a33b8fdbd7f87425e17ed8d..ac670bf730d2374730a42870f98319e2bd4f9368 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp
@@ -457,6 +457,13 @@ void PaintLayerClipper::calculateClipRectWithGeometryMapper(
   DCHECK(ancestorProperties && ancestorProperties->localBorderBoxProperties());
   PropertyTreeState destinationPropertyTreeState =
       *ancestorProperties->localBorderBoxProperties();
+  // CSS clip of the root is always applied.
+  if (ancestorProperties->cssClip()) {
+    DCHECK(destinationPropertyTreeState.clip() ==
+           ancestorProperties->cssClip());
+    destinationPropertyTreeState.setClip(
+        ancestorProperties->cssClip()->parent());
+  }
 
   if (&m_layer == context.rootLayer) {
     // Set the overflow clip for |propertyTreeState| so that it differs from