add getTextureHandle to SkSurface

src/image/SkSurface_Base.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSurface_Base_DEFINED
 #define SkSurface_Base_DEFINED
 
 #include "SkCanvas.h"
 #include "SkSurface.h"
 #include "SkSurfacePriv.h"
 
 class SkSurface_Base : public SkSurface {
 public:
     SkSurface_Base(int width, int height, const SkSurfaceProps*);
     SkSurface_Base(const SkImageInfo&, const SkSurfaceProps*);
     virtual ~SkSurface_Base();
 
+    virtual GrBackendObject onGetTextureHandle(ContentChangeMode) {
+        return 0;
+    }
+
     /**
      *  Allocate a canvas that will draw into this surface. We will cache this
      *  canvas, to return the same object to the caller multiple times. We
      *  take ownership, and will call unref() on the canvas when we go out of
      *  scope.
      */
     virtual SkCanvas* onNewCanvas() = 0;
 
     virtual SkSurface* onNewSurface(const SkImageInfo&) = 0;
 
@@ skipping 58 matching lines @@
 
 SkImage* SkSurface_Base::getCachedImage(Budgeted budgeted) {
     if (NULL == fCachedImage) {
         fCachedImage = this->onNewImageSnapshot(budgeted);
         SkASSERT(!fCachedCanvas || fCachedCanvas->getSurfaceBase() == this);
     }
     return fCachedImage;
 }
 
 #endif