some cleanup around GrGpu/GrDrawTarget copySurface

src/gpu/GrDrawTarget.cpp

Index: src/gpu/GrDrawTarget.cpp
diff --git a/src/gpu/GrDrawTarget.cpp b/src/gpu/GrDrawTarget.cpp
index bbf3eca05b4366b1de8727cf5a1b4963dc9f7556..9ac2d6a3b93e9d39123933760e74cbd0b19d0906 100644
--- a/src/gpu/GrDrawTarget.cpp
+++ b/src/gpu/GrDrawTarget.cpp
@@ -921,17 +921,20 @@ bool GrDrawTarget::copySurface(GrSurface* dst,
                                    dstPoint,
                                    &clippedSrcRect,
                                    &clippedDstPoint)) {
-        SkASSERT(GrDrawTarget::canCopySurface(dst, src, srcRect, dstPoint));
         return true;
     }
 
-    if (!GrDrawTarget::canCopySurface(dst, src, clippedSrcRect, clippedDstPoint)) {
-        return false;
+    if (this->onCopySurface(dst, src, clippedSrcRect, clippedDstPoint)) {
+        return true;
     }
 
     GrRenderTarget* rt = dst->asRenderTarget();
     GrTexture* tex = src->asTexture();
 
+    if ((dst == src) || !rt || !tex) {
+        return false;
+    }
+
     GrDrawState drawState;
     drawState.setRenderTarget(rt);
     SkMatrix matrix;
@@ -965,7 +968,13 @@ bool GrDrawTarget::canCopySurface(const GrSurface* dst,
                                    &clippedDstPoint)) {
         return true;
     }
+    return this->internalCanCopySurface(dst, src, clippedSrcRect, clippedDstPoint);
+}
 
+bool GrDrawTarget::internalCanCopySurface(const GrSurface* dst,
+                                          const GrSurface* src,
+                                          const SkIRect& clippedSrcRect,
+                                          const SkIPoint& clippedDstPoint) {
     // Check that the read/write rects are contained within the src/dst bounds.
     SkASSERT(!clippedSrcRect.isEmpty());
     SkASSERT(SkIRect::MakeWH(src->width(), src->height()).contains(clippedSrcRect));
@@ -973,14 +982,9 @@ bool GrDrawTarget::canCopySurface(const GrSurface* dst,
     SkASSERT(clippedDstPoint.fX + clippedSrcRect.width() <= dst->width() &&
              clippedDstPoint.fY + clippedSrcRect.height() <= dst->height());
 
-    return (dst != src) && dst->asRenderTarget() && src->asTexture();
-}
-
-void GrDrawTarget::initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) {
-    // Make the dst of the copy be a render target because the default copySurface draws to the dst.
-    desc->fOrigin = kDefault_GrSurfaceOrigin;
-    desc->fFlags = kRenderTarget_GrSurfaceFlag | kNoStencil_GrSurfaceFlag;
-    desc->fConfig = src->config();
+    // The base class can do it as a draw or the subclass may be able to handle it.
+    return ((dst != src) && dst->asRenderTarget() && src->asTexture()) ||
+           this->onCanCopySurface(dst, src, clippedSrcRect, clippedDstPoint);
 }
 
 ///////////////////////////////////////////////////////////////////////////////