Revert of GrContext::copyTexture->GrContext::copySurface. Add a flush writes pixel ops flag. (patchset #3 id:40001 of https://codereview.chromium.org/622663002/)

Reason for revert:
Breaking GMs on some bots

Original issue's description:
> GrContext::copyTexture->GrContext::copySurface.
>
> Add a flush writes pixel ops flag.
>
> Add an explicit flush writes for GrSurface.
>
> BUG=skia:2977
>
> Committed: https://skia.googlesource.com/skia/+/cf99b00980b6c9c557e71abf1a7c9f9b21217262

TBR=robertphillips@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:2977

Review URL: https://codereview.chromium.org/621073002
diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index 67e8dd3..6ca67bc 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -297,8 +297,7 @@
                                              SkImageInfo2GrPixelConfig(bm.colorType(),
                                                                        bm.alphaType()),
                                              bm.getPixels(),
-                                             bm.rowBytes(),
-                                             GrContext::kFlushWrites_PixelOp);
+                                             bm.rowBytes());
             }
         }
 #endif