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

src/gpu/batches/GrCopySurfaceBatch.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrCopySurfaceBatch_DEFINED
 #define GrCopySurfaceBatch_DEFINED
 
 #include "GrBatch.h"
 #include "GrBatchFlushState.h"
 #include "GrGpu.h"
 #include "GrRenderTarget.h"
 
 class GrCopySurfaceBatch final : public GrBatch {
 public:
     DEFINE_BATCH_CLASS_ID
 
+    /** This should not really be exposed as Create() will apply this clipping, but there is
+     *  currently a workaround in GrContext::copySurface() for non-render target dsts that relies
+     *  on it. */
+    static bool ClipSrcRectAndDstPoint(const GrSurface* dst,
+                                       const GrSurface* src,
+                                       const SkIRect& srcRect,
+                                       const SkIPoint& dstPoint,
+                                       SkIRect* clippedSrcRect,
+                                       SkIPoint* clippedDstPoint);
+
     static GrBatch* Create(GrSurface* dst, GrSurface* src, const SkIRect& srcRect,
                            const SkIPoint& dstPoint);
 
     const char* name() const override { return "CopySurface"; }
 
     uint32_t renderTargetUniqueID() const override {
         GrRenderTarget* rt = fDst.get()->asRenderTarget();
         return rt ? rt->getUniqueID() : 0;
     }
     GrRenderTarget* renderTarget() const override { return fDst.get()->asRenderTarget(); }
@@ skipping 29 matching lines @@
 
     GrPendingIOResource<GrSurface, kWrite_GrIOType> fDst;
     GrPendingIOResource<GrSurface, kRead_GrIOType>  fSrc;
     SkIRect                                         fSrcRect;
     SkIPoint                                        fDstPoint;
 
     typedef GrBatch INHERITED;
 };
 
 #endif