Apply both phsical bounding box and clip to composited bounds.

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 970f6567235e582a7edfe79317f5618b48f01000..2146ec37fff702c9672c646f6c04d27b07ea09eb 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -2551,13 +2551,10 @@ LayoutRect PaintLayer::boundingBoxForCompositingInternal(
   const_cast<PaintLayer*>(this)->stackingNode()->updateLayerListsIfNeeded();
 
   // If there is a clip applied by an ancestor to this PaintLayer but below or
-  // equal to |ancestorLayer|, use that clip as the bounds rather than the
-  // recursive bounding boxes, since the latter may be larger than the actual
-  // size. See https://bugs.webkit.org/show_bug.cgi?id=80372 for examples.
+  // equal to |ancestorLayer|, apply that clip.
   LayoutRect result = clipper().localClipRect(compositedLayer);
-  // TODO(chrishtr): avoid converting to IntRect and back.
-  if (result == LayoutRect(LayoutRect::infiniteIntRect()))
-    result = physicalBoundingBox(LayoutPoint());
+
+  result.intersect(physicalBoundingBox(LayoutPoint()));
 
   expandRectForStackingChildren(compositedLayer, result, options);