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

include/gpu/GrRenderTarget.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrRenderTarget_DEFINED
 #define GrRenderTarget_DEFINED
 
@@ skipping 131 matching lines @@
                    bool isWrapped,
                    GrTexture* texture,
                    const GrTextureDesc& desc)
         : INHERITED(gpu, isWrapped, desc)
         , fStencilBuffer(NULL)
         , fTexture(texture) {
         fResolveRect.setLargestInverted();
     }
 
     friend class GrTexture;
-    // When a texture unrefs an owned render target this func
-    // removes the back pointer. This could be called from
-    // texture's destructor but would have to be done in derived
-    // classes. By the time of texture base destructor it has already
-    // lost its pointer to the rt.
-    void onTextureReleaseRenderTarget() {
-        GrAssert(NULL != fTexture);
-        fTexture = NULL;
-    }
 
     // override of GrResource
     virtual void onAbandon() SK_OVERRIDE;
     virtual void onRelease() SK_OVERRIDE;
 
 private:
     GrStencilBuffer*  fStencilBuffer;
     GrTexture*        fTexture; // not ref'ed
 
     GrIRect           fResolveRect;
 
     typedef GrSurface INHERITED;
 };
 
 #endif