Apply CSS clip to foreground and background clip rects.

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 439 matching lines @@
   DCHECK(m_geometryMapper);
   const auto* properties = m_layer.layoutObject().paintProperties();
   DCHECK(properties && properties->localBorderBoxProperties());
 
   PropertyTreeState propertyTreeState = *properties->localBorderBoxProperties();
   const auto* ancestorProperties =
       context.rootLayer->layoutObject().paintProperties();
   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
     // |destinationPropertyTreeState| in its clip.
     if (isForeground && context.respectOverflowClip == RespectOverflowClip &&
         properties->overflowClip())
       propertyTreeState.setClip(properties->overflowClip());
   } else {
     // Set the clip of |destinationPropertyTreeState| to be inside the
     // ancestor's overflow clip, so that that clip is not applied.
@@ skipping 119 matching lines @@
   DCHECK(!m_geometryMapper);
   ClipRectsContext context(rootLayer, PaintingClipRects,
                            IgnorePlatformOverlayScrollbarSize,
                            subpixelAccumulation);
   if (respectOverflowClip == IgnoreOverflowClip)
     context.setIgnoreOverflowClip();
   return getClipRects(context);
 }
 
 }  // namespace blink