Remove GrTexture::releaseRenderTarget() and add GrSurface::isSameAs().

include/gpu/GrSurface.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 GrSurface_DEFINED
 #define GrSurface_DEFINED
@@ skipping 46 matching lines @@
     virtual GrTexture* asTexture() = 0;
     virtual const GrTexture* asTexture() const = 0;
 
     /**
      * @return the render target underlying this surface, may be NULL.
      */
     virtual GrRenderTarget* asRenderTarget() = 0;
     virtual const GrRenderTarget* asRenderTarget() const = 0;
 
     /**
+     * Checks whether this GrSurface refers to the same GPU object as other. This
+     * catches the case where a GrTexture and GrRenderTarget refer to the same
+     * GPU memory.
+     */
+    bool isSameAs(const GrSurface* other) const {
+        const GrRenderTarget* thisRT = this->asRenderTarget();
+        if (NULL != thisRT) {
+            return thisRT == other->asRenderTarget();
+        } else {
+            const GrTexture* thisTex = this->asTexture();
+            GrAssert(NULL != thisTex); // We must be one or the other
+            return thisTex == other->asTexture();
+        }
+    }
+
+    /**
      * Reads a rectangle of pixels from the surface.
      * @param left          left edge of the rectangle to read (inclusive)
      * @param top           top edge of the rectangle to read (inclusive)
      * @param width         width of rectangle to read in pixels.
      * @param height        height of rectangle to read in pixels.
      * @param config        the pixel config of the destination buffer
      * @param buffer        memory to read the rectangle into.
      * @param rowBytes      number of bytes between consecutive rows. Zero means rows are tightly
      *                      packed.
      * @param pixelOpsFlags See the GrContext::PixelOpsFlags enum.
@@ skipping 32 matching lines @@
     , fDesc(desc) {
     }
 
     GrTextureDesc fDesc;
 
 private:
     typedef GrResource INHERITED;
 };
 
 #endif // GrSurface_DEFINED