add getTextureHandle to SkSurface

include/core/SkSurface.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_DEFINED
 #define SkSurface_DEFINED
 
@@ skipping 120 matching lines @@
         /**
          *  Use this mode if prior surface contents need to be preserved or
          *  if in doubt.
          */
         kRetain_ContentChangeMode,
     };
 
     /**
      *  Call this if the contents are about to change. This will (lazily) force a new
      *  value to be returned from generationID() when it is called next.
+     *
+     *  CAN WE DEPRECATE THIS?
      */
     void notifyContentWillChange(ContentChangeMode mode);
 
+    enum TextureHandleAccess {
+        kFlushRead_TextureHandleAccess,     //!< caller may read from the texture
+        kFlushWrite_TextureHandleAccess,    //!< caller may write to the texture
+        kDiscardWrite_TextureHandleAccess,  //!< caller must over-write the entire texture
+    };
+    /**
+     *  Retrieves the backend API handle of the texture used by this surface, or 0 if the surface
+     *  is not backed by a GPU texture.
+     *
+     *  The returned texture-handle is only valid until the next draw-call into the surface,
+     *  or the surface is deleted.
+     */
+    GrBackendObject getTextureHandle(TextureHandleAccess);
+
     /**
      *  Return a canvas that will draw into this surface. This will always
      *  return the same canvas for a given surface, and is manged/owned by the
      *  surface. It should not be used when its parent surface has gone out of
      *  scope.
      */
     SkCanvas* getCanvas();
 
     /**
      *  Return a new surface that is "compatible" with this one, in that it will
@@ skipping 75 matching lines @@
 private:
     const SkSurfaceProps fProps;
     const int            fWidth;
     const int            fHeight;
     uint32_t             fGenerationID;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif