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

Source/core/paint/FloatClipRecorder.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 FloatClipRecorder_h
 #define FloatClipRecorder_h
 
 #include "core/paint/PaintPhase.h"
 #include "platform/geometry/FloatRect.h"
 #include "platform/graphics/paint/DisplayItem.h"
 
 namespace blink {
 
 class FloatClipRecorder {
 public:
+    FloatClipRecorder(GraphicsContext&, const DisplayItemClientWrapper&, PaintPhase);
     FloatClipRecorder(GraphicsContext&, const DisplayItemClientWrapper&, PaintPhase, const FloatRect&);
+    ~FloatClipRecorder();
 
-    ~FloatClipRecorder();
+    void begin(const FloatRect&);
 
 private:
     GraphicsContext& m_context;
     DisplayItemClientWrapper m_client;
     DisplayItem::Type m_clipType;
+    bool m_engaged;
 };
 
 } // namespace blink
 
 #endif // FloatClipRecorder_h