WIP RasterCanvasLayerAllocator experiment 2

include/core/SkCanvas.h

Index: include/core/SkCanvas.h
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index d28d0f18982292a0c4294cd032db3590ad4cad50..5e7ca1f4df775a507e9b3222082236cf2a072e33 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -13,6 +13,7 @@
 #include "SkDeque.h"
 #include "SkImage.h"
 #include "SkPaint.h"
+#include "SkRasterCanvasLayerAllocator.h"
 #include "SkRefCnt.h"
 #include "SkRegion.h"
 #include "SkSurfaceProps.h"
@@ -102,6 +103,8 @@ public:
     */
     explicit SkCanvas(SkBaseDevice* device);
 
+    explicit SkCanvas(SkBaseDevice* device, SkRasterCanvasLayerAllocator*);
+
     /** Construct a canvas with the specified bitmap to draw into.
         @param bitmap   Specifies a bitmap for the canvas to draw into. Its
                         structure are copied to the canvas.
@@ -132,6 +135,8 @@ public:
      */
     bool getProps(SkSurfaceProps*) const;
 
+    SkRasterCanvasLayerAllocator* getLayerAllocator() const { return fLayerAllocator.get(); }
+
     ///////////////////////////////////////////////////////////////////////////
 
     /**
@@ -1689,6 +1694,8 @@ private:
     void validateClip() const {}
 #endif
 
+    std::unique_ptr<SkRasterCanvasLayerAllocator> fLayerAllocator;
+
     typedef SkRefCnt INHERITED;
 };