Add SkCanvasStack and update the Canvas utilities to use it.

include/utils/SkNWayCanvas.h

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkNWayCanvas_DEFINED
 #define SkNWayCanvas_DEFINED
 
 #include "SkCanvas.h"
 
 class SK_API SkNWayCanvas : public SkCanvas {
 public:
     SkNWayCanvas(int width, int height);
     virtual ~SkNWayCanvas();
 
-    void addCanvas(SkCanvas*);
-    void removeCanvas(SkCanvas*);
-    void removeAll();
+    virtual void addCanvas(SkCanvas*);
+    virtual void removeCanvas(SkCanvas*);
+    virtual void removeAll();
 
     ///////////////////////////////////////////////////////////////////////////
     // These are forwarded to the N canvases we're referencing
 
     virtual int save(SaveFlags) SK_OVERRIDE;
     virtual int saveLayer(const SkRect* bounds, const SkPaint*,
                           SaveFlags) SK_OVERRIDE;
     virtual void restore() SK_OVERRIDE;
     virtual bool translate(SkScalar dx, SkScalar dy) SK_OVERRIDE;
     virtual bool scale(SkScalar sx, SkScalar sy) SK_OVERRIDE;
@@ skipping 40 matching lines @@
                               const uint16_t indices[], int indexCount,
                               const SkPaint&) SK_OVERRIDE;
 
     virtual SkBounder* setBounder(SkBounder*) SK_OVERRIDE;
     virtual SkDrawFilter* setDrawFilter(SkDrawFilter*) SK_OVERRIDE;
 
     virtual void beginCommentGroup(const char* description) SK_OVERRIDE;
     virtual void addComment(const char* kywd, const char* value) SK_OVERRIDE;
     virtual void endCommentGroup() SK_OVERRIDE;
 
-private:
+protected:
     SkTDArray<SkCanvas*> fList;
 
     class Iter;
 
+private:
     typedef SkCanvas INHERITED;
 };
 
 
 #endif