Swap render target instead of creating a new gpu device for surface copy-on-write

include/core/SkCanvas.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvas_DEFINED
 #define SkCanvas_DEFINED
 
@@ skipping 1288 matching lines @@
     friend class SkCanvasStateUtils;
 
     // call this each time we attach ourselves to a device
     //  - constructor
     //  - internalSaveLayer
     void setupDevice(SkBaseDevice*);
 
     SkBaseDevice* init(SkBaseDevice*, InitFlags);
 
     /**
-     *  DEPRECATED
-     *
-     *  Specify a device for this canvas to draw into. If it is not null, its
-     *  reference count is incremented. If the canvas was already holding a
-     *  device, its reference count is decremented. The new device is returned.
-     */
-    SkBaseDevice* setRootDevice(SkBaseDevice* device);
-
-    /**
      * Gets the size/origin of the top level layer in global canvas coordinates. We don't want this
      * to be public because it exposes decisions about layer sizes that are internal to the canvas.
      */
     SkISize getTopLayerSize() const;
     SkIPoint getTopLayerOrigin() const;
 
     // internal methods are not virtual, so they can safely be called by other
     // canvas apis, without confusing subclasses (like SkPictureRecording)
     void internalDrawBitmap(const SkBitmap&, const SkMatrix& m, const SkPaint* paint);
     void internalDrawBitmapRect(const SkBitmap& bitmap, const SkRect* src,
@@ skipping 172 matching lines @@
 
 class SkCanvasClipVisitor {
 public:
     virtual ~SkCanvasClipVisitor();
     virtual void clipRect(const SkRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipRRect(const SkRRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) = 0;
 };
 
 #endif