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

Source/core/paint/RoundedInnerRectClipper.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef RoundedInnerRectClipper_h
 #define RoundedInnerRectClipper_h
 
 #include "platform/graphics/paint/DisplayItem.h"
 
 namespace blink {
 
 class FloatRoundedRect;
 class LayoutRect;
 class LayoutObject;
 struct PaintInfo;
 
 enum RoundedInnerRectClipperBehavior {
     ApplyToDisplayListIfEnabled,
     ApplyToContext
 };
 
 class RoundedInnerRectClipper {
 public:
+    RoundedInnerRectClipper(LayoutObject&, const PaintInfo&);
     RoundedInnerRectClipper(LayoutObject&, const PaintInfo&, const LayoutRect&, const FloatRoundedRect& clipRect, RoundedInnerRectClipperBehavior);
     ~RoundedInnerRectClipper();
 
+    void begin(const LayoutRect&, const FloatRoundedRect& clipRect, RoundedInnerRectClipperBehavior);
+
 private:
     LayoutObject& m_layoutObject;
     const PaintInfo& m_paintInfo;
+
+    // Valid only if |m_engaged| is true.
     bool m_useDisplayItemList;
     DisplayItem::Type m_clipType;
+
+    bool m_engaged;
 };
 
 } // namespace blink
 
 #endif // RoundedInnerRectClipper_h