Fix border radius on composited children.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.h b/third_party/WebKit/Source/core/paint/PaintLayerPainter.h
index b767e7a5d41d579d0c8b88d959678c5574516c12..e802d63a5384e5950c35b5cb89ad1dc1f5e390c2 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayerPainter.h
@@ -139,6 +139,11 @@ class CORE_EXPORT PaintLayerPainter {
   bool shouldPaintLayerInSoftwareMode(const GlobalPaintFlags,
                                       PaintLayerFlags paintFlags);
 
+  // Convert a fragmentOffset from the coordinate system of this painter's
+  // layer to the coordinate system of the layer in which it's border radius
+  // clip rect is defined, for painting composited children using mask layers.
+  LayoutPoint fragmentOffsetForAncestorClipMask(const LayoutPoint&);
+
   PaintLayer& m_paintLayer;
 };