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

Source/platform/graphics/paint/ClipRecorder.h

 // Copyright 2014 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 ClipRecorder_h
 #define ClipRecorder_h
 
 #include "SkRegion.h"
 #include "platform/geometry/LayoutRect.h"
 #include "platform/graphics/paint/DisplayItem.h"
 
 namespace blink {
 
 class GraphicsContext;
 
 class PLATFORM_EXPORT ClipRecorder {
     WTF_MAKE_FAST_ALLOCATED(ClipRecorder);
 public:
+    ClipRecorder(GraphicsContext&, const DisplayItemClientWrapper&, DisplayItem::Type);
     ClipRecorder(GraphicsContext&, const DisplayItemClientWrapper&, DisplayItem::Type, const LayoutRect& clipRect, SkRegion::Op = SkRegion::kIntersect_Op);
     ~ClipRecorder();
+
+    void begin(const LayoutRect& clipRect, SkRegion::Op = SkRegion::kIntersect_Op);
 private:
     DisplayItemClientWrapper m_client;
     GraphicsContext& m_context;
     DisplayItem::Type m_type;
+    bool m_engaged;
 };
 
 } // namespace blink
 
 #endif // ClipRecorder_h