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

Source/core/paint/CompositingRecorder.h

Index: Source/core/paint/CompositingRecorder.h
diff --git a/Source/core/paint/CompositingRecorder.h b/Source/core/paint/CompositingRecorder.h
index b5982753cc62a65d94f523bbd980c294506c08db..ff84fd63e60b1ef1159e40db4609f5427fcc2d52 100644
--- a/Source/core/paint/CompositingRecorder.h
+++ b/Source/core/paint/CompositingRecorder.h
@@ -17,10 +17,12 @@ class LayoutObject;
 
 class CompositingRecorder {
 public:
-    CompositingRecorder(GraphicsContext&, const DisplayItemClientWrapper&, const SkXfermode::Mode, const float opacity, const FloatRect* bounds = 0, ColorFilter = ColorFilterNone);
-
+    CompositingRecorder(GraphicsContext&, const DisplayItemClientWrapper&);
+    CompositingRecorder(GraphicsContext&, const DisplayItemClientWrapper&, SkXfermode::Mode, float opacity, const FloatRect* bounds = 0, ColorFilter = ColorFilterNone);
     ~CompositingRecorder();
 
+    void begin(SkXfermode::Mode, float opacity, const FloatRect* bounds = 0, ColorFilter = ColorFilterNone);
+
     // FIXME: These helpers only exist to ease the transition to slimming paint
     //        and should be removed once slimming paint is enabled by default.
     static void beginCompositing(GraphicsContext&, const DisplayItemClientWrapper&, const SkXfermode::Mode, const float opacity, const FloatRect* bounds = 0, ColorFilter = ColorFilterNone);
@@ -29,6 +31,7 @@ public:
 private:
     DisplayItemClientWrapper m_client;
     GraphicsContext& m_graphicsContext;
+    bool m_engaged;
 };
 
 } // namespace blink