Reland of duce copying of local data structures in GeometryMapper and PaintLayerClipper.

third_party/WebKit/Source/core/paint/PaintLayerClipper.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 165 matching lines @@
 
   void clearClipRectsIncludingDescendants();
   void clearClipRectsIncludingDescendants(ClipRectsCacheSlot);
 
   // Returns the background clip rect of the layer in the local coordinate
   // space. Only looks for clips up to the given ancestor.
   LayoutRect localClipRect(const PaintLayer& ancestorLayer) const;
 
   // Computes the same thing as backgroundRect in calculateRects(), but skips
   // applying CSS clip and the visualOverflowRect() of |m_layer|.
-  ClipRect backgroundClipRect(const ClipRectsContext&) const;
+  void calculateBackgroundClipRect(const ClipRectsContext&,
+                                   ClipRect& output) const;
 
   // This method figures out our layerBounds in coordinates relative to
   // |rootLayer|. It also computes our background and foreground clip rects
   // for painting/event handling. Pass offsetFromRoot if known.
   void calculateRects(const ClipRectsContext&,
                       const LayoutRect& paintDirtyRect,
                       LayoutRect& layerBounds,
                       ClipRect& backgroundRect,
                       ClipRect& foregroundRect,
                       const LayoutPoint* offsetFromRoot = 0) const;
@@ skipping 10 matching lines @@
   ClipRects* clipRectsIfCached(const ClipRectsContext&) const;
   ClipRects& storeClipRectsInCache(const ClipRectsContext&,
                                    ClipRects* parentClipRects,
                                    const ClipRects&) const;
 
   void getOrCalculateClipRects(const ClipRectsContext&, ClipRects&) const;
 
   bool shouldClipOverflow(const ClipRectsContext&) const;
   bool shouldRespectOverflowClip(const ClipRectsContext&) const;
 
-  // Returned clip rect is in the space of the context's rootLayer.
-  ClipRect clipRectWithGeometryMapper(const ClipRectsContext&,
-                                      bool isForeground) const;
+  // Returned clip rect in |output| is in the space of the context's rootLayer.
+  void calculateClipRectWithGeometryMapper(const ClipRectsContext&,
+                                           bool isForeground,
+                                           ClipRect& output) const;
   // Mutates the given rect into a rect in the space of the context's
   // rootLayer.
   void mapLocalToRootWithGeometryMapper(const ClipRectsContext&,
                                         LayoutRect&) const;
   // Same as calculateRects, but using GeometryMapper.
   void calculateRectsWithGeometryMapper(
       const ClipRectsContext&,
       const LayoutRect& paintDirtyRect,
       LayoutRect& layerBounds,
       ClipRect& backgroundRect,
       ClipRect& foregroundRect,
       const LayoutPoint* offsetFromRoot = 0) const;
 
   void applyOverflowClipToBackgroundRectWithGeometryMapper(
       const ClipRectsContext&,
       ClipRect&) const;
 
   const PaintLayer& m_layer;
   GeometryMapper* m_geometryMapper;
 
   friend class PaintLayerClipperTest;
 };
 
 }  // namespace blink
 
 #endif  // LayerClipper_h