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

Source/core/paint/ScrollRecorder.h

Index: Source/core/paint/ScrollRecorder.h
diff --git a/Source/core/paint/ScrollRecorder.h b/Source/core/paint/ScrollRecorder.h
index f0421a28316f36ce37a9e9f39a0b1aede24152ae..46f564b00480b3eba6f4b488d5b5d7855494d982 100644
--- a/Source/core/paint/ScrollRecorder.h
+++ b/Source/core/paint/ScrollRecorder.h
@@ -9,6 +9,7 @@
 #include "core/paint/PaintPhase.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/paint/DisplayItem.h"
+#include "platform/heap/GarbageCollected.h"
 #include "wtf/FastAllocBase.h"
 
 namespace blink {
@@ -20,12 +21,15 @@ class GraphicsContext;
 class CORE_EXPORT ScrollRecorder {
     WTF_MAKE_FAST_ALLOCATED(ScrollRecorder);
 public:
+    ScrollRecorder(GraphicsContext&, const DisplayItemClientWrapper&, PaintPhase);
     ScrollRecorder(GraphicsContext&, const DisplayItemClientWrapper&, PaintPhase, const IntSize& currentOffset);
     ~ScrollRecorder();
+    void begin(const IntSize& currentOffset);
 private:
     DisplayItemClientWrapper m_client;
     DisplayItem::Type m_beginItemType;
     GraphicsContext& m_context;
+    bool m_engaged;
 };
 
 } // namespace blink