Add auto purging for SkPicture-related Ganesh resources (esp. layers)

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 946 matching lines @@
                                 const SkPaint& paint);
 
     /** PRIVATE / EXPERIMENTAL -- do not call
         Perform back-end analysis/optimization of a picture. This may attach
         optimization data to the picture which can be used by a later
         drawPicture call.
         @param picture The recorded drawing commands to analyze/optimize
     */
     void EXPERIMENTAL_optimize(const SkPicture* picture);
 
-    /** PRIVATE / EXPERIMENTAL -- do not call
-        Purge all the discardable optimization information associated with
-        'picture'. If NULL is passed in, purge all discardable information.
-    */
-    void EXPERIMENTAL_purge(const SkPicture* picture);
-
     /** Draw the picture into this canvas. This method effective brackets the
         playback of the picture's draw calls with save/restore, so the state
         of this canvas will be unchanged after this call.
         @param picture The recorded drawing commands to playback into this
                        canvas.
     */
     void drawPicture(const SkPicture* picture);
 
     enum VertexMode {
         kTriangles_VertexMode,
@@ skipping 495 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