Use the bounding box of all descendants for localVisualRect if there is a mask.

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

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. 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 406 matching lines @@
   };
 
   // Bounding box relative to some ancestor layer. Pass offsetFromRoot if known.
   LayoutRect physicalBoundingBox(const LayoutPoint& offsetFromRoot) const;
   LayoutRect physicalBoundingBox(const PaintLayer* ancestorLayer) const;
   LayoutRect physicalBoundingBoxIncludingStackingChildren(
       const LayoutPoint& offsetFromRoot,
       CalculateBoundsOptions = MaybeIncludeTransformForAncestorLayer) const;
   LayoutRect fragmentsBoundingBox(const PaintLayer* ancestorLayer) const;
 
-  FloatRect boxForFilter() const;
+  FloatRect boxForFilterOrMask() const;
   LayoutRect boxForClipPath() const;
 
   LayoutRect boundingBoxForCompositingOverlapTest() const;
 
   // If true, this layer's children are included in its bounds for overlap
   // testing.  We can't rely on the children's positions if this layer has a
   // filter that could have moved the children's pixels around.
   bool overlapBoundsIncludeChildren() const;
   LayoutRect boundingBoxForCompositing(
       const PaintLayer* ancestorLayer = 0,
@@ skipping 786 matching lines @@
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLayerTree(const blink::PaintLayer*);
 CORE_EXPORT void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif  // Layer_h