Make PaintLayerClipper objects transient

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 131 matching lines @@
 // depending on the 'position' of the elements.
 //
 // Now instead if we add "clip: rect(0px, 100px, 100px, 0px)" to #container,
 // the clip will apply to both #inflow and #fixed. That's because 'clip'
 // applies to any descendant, regardless of containing blocks. Note that
 // #container and #fixed are siblings in the paint tree but #container does
 // clip #fixed. This is the reason why we compute the painting clip rects during
 // a layout tree walk and cache them for painting.
 class CORE_EXPORT PaintLayerClipper {
     DISALLOW_NEW();
-    WTF_MAKE_NONCOPYABLE(PaintLayerClipper);
 public:
-    explicit PaintLayerClipper(const LayoutBoxModelObject&);
+    explicit PaintLayerClipper(const PaintLayer& layer) : m_layer(layer) { }
 
     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;
 
     ClipRect backgroundClipRect(const ClipRectsContext&) 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;
 
-    ClipRects* paintingClipRects(const PaintLayer* rootLayer, ShouldRespectOverflowClip, const LayoutSize& subpixelAccumulation) const;
+    ClipRects& paintingClipRects(const PaintLayer* rootLayer, ShouldRespectOverflowClip, const LayoutSize& subpixelAccumulation) const;
 
 private:
-    ClipRects* getClipRects(const ClipRectsContext&) const;
+    ClipRects& getClipRects(const ClipRectsContext&) const;
 
     void calculateClipRects(const ClipRectsContext&, ClipRects&) const;
     ClipRects* clipRectsIfCached(const ClipRectsContext&) const;
-    ClipRects* storeClipRectsInCache(const ClipRectsContext&, ClipRects* parentClipRects, const ClipRects&) const;
+    ClipRects& storeClipRectsInCache(const ClipRectsContext&, ClipRects* parentClipRects, const ClipRects&) const;
 
-    // cachedClipRects looks buggy: It doesn't check whether context.rootLayer and entry.root match.
-    // FIXME: Move callers to clipRectsIfCached, which does the proper checks.
-    ClipRects* cachedClipRects(const ClipRectsContext& context) const
-    {
-        return m_cache ? m_cache->get(context.cacheSlot()).clipRects.get() : 0;
-    }
     void getOrCalculateClipRects(const ClipRectsContext&, ClipRects&) const;
 
-    ClipRectsCache& cache() const
-    {
-        if (!m_cache)
-            m_cache = adoptPtr(new ClipRectsCache);
-        return *m_cache;
-    }
-
     bool shouldRespectOverflowClip(const ClipRectsContext&) const;
 
-    // FIXME: Could this be a LayoutBox?
-    const LayoutBoxModelObject& m_layoutObject;
-
-    // Lazily created by 'cache() const'.
-    mutable OwnPtr<ClipRectsCache> m_cache;
+    const PaintLayer& m_layer;
 };
 
 } // namespace blink
 
 #endif // LayerClipper_h