Allow certain SP recorder classes to defer their "begin" operation.

Source/core/paint/LayerClipRecorder.h

Index: Source/core/paint/LayerClipRecorder.h
diff --git a/Source/core/paint/LayerClipRecorder.h b/Source/core/paint/LayerClipRecorder.h
index 517c9a35d88df6abc9dd55a234d5f752e773d8fa..55aecb67e7bc7b0c2709f476817b4211eb0625fd 100644
--- a/Source/core/paint/LayerClipRecorder.h
+++ b/Source/core/paint/LayerClipRecorder.h
@@ -34,18 +34,21 @@ public:
     // same time we pass a fragmentOffset, so that we can translate from flow thread coordinates to
     // visual coordinates. This may look rather confusing/redundant, but it is needed for rounded
     // border clipping. Would be nice to clean up this.
-    explicit LayerClipRecorder(GraphicsContext&, const LayoutBoxModelObject&, DisplayItem::Type, const ClipRect&, const DeprecatedPaintLayerPaintingInfo* localPaintingInfo, const LayoutPoint& fragmentOffset, PaintLayerFlags, BorderRadiusClippingRule = IncludeSelfForBorderRadius);
-
+    LayerClipRecorder(GraphicsContext&, DisplayItem::Type);
+    LayerClipRecorder(GraphicsContext&, const LayoutBoxModelObject&, DisplayItem::Type, const ClipRect&, const DeprecatedPaintLayerPaintingInfo* localPaintingInfo, const LayoutPoint& fragmentOffset, PaintLayerFlags, BorderRadiusClippingRule = IncludeSelfForBorderRadius);
     ~LayerClipRecorder();
 
+    void begin(const LayoutBoxModelObject& layoutObject, const ClipRect&, const DeprecatedPaintLayerPaintingInfo* localPaintingInfo, const LayoutPoint& fragmentOffset, PaintLayerFlags, BorderRadiusClippingRule = IncludeSelfForBorderRadius);
+
 private:
 
     void collectRoundedRectClips(DeprecatedPaintLayer&, const DeprecatedPaintLayerPaintingInfo& localPaintingInfo, GraphicsContext&, const LayoutPoint& fragmentOffset, PaintLayerFlags,
         BorderRadiusClippingRule, Vector<FloatRoundedRect>& roundedRectClips);
 
     GraphicsContext& m_graphicsContext;
-    const LayoutBoxModelObject& m_layoutObject;
+    const LayoutBoxModelObject* m_layoutObject;
     DisplayItem::Type m_clipType;
+    bool m_engaged;
 };
 
 } // namespace blink