Make copySurface work for texture dsts, return a bool, & add unit test.

src/gpu/GrDrawTarget.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDrawTarget_DEFINED
 #define GrDrawTarget_DEFINED
 
@@ skipping 126 matching lines @@
     /**
      * Copies a pixel rectangle from one surface to another. This call may finalize
      * reserved vertex/index data (as though a draw call was made). The src pixels
      * copied are specified by srcRect. They are copied to a rect of the same
      * size in dst with top left at dstPoint. If the src rect is clipped by the
      * src bounds then  pixel values in the dst rect corresponding to area clipped
      * by the src rect are not overwritten. This method is not guaranteed to succeed
      * depending on the type of surface, configs, etc, and the backend-specific
      * limitations.
      */
-    void copySurface(GrSurface* dst,
+    bool copySurface(GrSurface* dst,
                      GrSurface* src,
                      const SkIRect& srcRect,
                      const SkIPoint& dstPoint);
 
     /** Provides access to internal functions to GrClipMaskManager without friending all of
         GrDrawTarget to CMM. */
     class CMMAccess {
     public:
         CMMAccess(GrDrawTarget* drawTarget) : fDrawTarget(drawTarget) {}
     private:
@@ skipping 100 matching lines @@
     SkTDArray<GrDrawTarget*>                    fDependencies;
     GrRenderTarget*                             fRenderTarget;
 
     bool                                        fDrawBatchBounds;
     int                                         fMaxBatchLookback;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif