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

src/gpu/batches/GrCopySurfaceBatch.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrCopySurfaceBatch.h"
 
 // returns true if the read/written rect intersects the src/dst and false if not.
-static bool clip_srcrect_and_dstpoint(const GrSurface* dst,
-                                      const GrSurface* src,
-                                      const SkIRect& srcRect,
-                                      const SkIPoint& dstPoint,
-                                      SkIRect* clippedSrcRect,
-                                      SkIPoint* clippedDstPoint) {
+bool GrCopySurfaceBatch::ClipSrcRectAndDstPoint(const GrSurface* dst,
+                                                const GrSurface* src,
+                                                const SkIRect& srcRect,
+                                                const SkIPoint& dstPoint,
+                                                SkIRect* clippedSrcRect,
+                                                SkIPoint* clippedDstPoint) {
     *clippedSrcRect = srcRect;
     *clippedDstPoint = dstPoint;
 
     // clip the left edge to src and dst bounds, adjusting dstPoint if necessary
     if (clippedSrcRect->fLeft < 0) {
         clippedDstPoint->fX -= clippedSrcRect->fLeft;
         clippedSrcRect->fLeft = 0;
     }
     if (clippedDstPoint->fX < 0) {
         clippedSrcRect->fLeft -= clippedDstPoint->fX;
@@ skipping 32 matching lines @@
 }
 
 GrBatch* GrCopySurfaceBatch::Create(GrSurface* dst, GrSurface* src, const SkIRect& srcRect,
                                     const SkIPoint& dstPoint) {
     SkASSERT(dst);
     SkASSERT(src);
 
     SkIRect clippedSrcRect;
     SkIPoint clippedDstPoint;
     // If the rect is outside the src or dst then we've already succeeded.
-    if (!clip_srcrect_and_dstpoint(dst,
-                                    src,
-                                    srcRect,
-                                    dstPoint,
-                                    &clippedSrcRect,
-                                    &clippedDstPoint)) {
+    if (!ClipSrcRectAndDstPoint(dst, src, srcRect, dstPoint, &clippedSrcRect, &clippedDstPoint)) {
         return nullptr;
     }
     return new GrCopySurfaceBatch(dst, src, clippedSrcRect, clippedDstPoint);
 }