Pass the writeView as a const-ref instead of a pointer …

The important part is in GrOpFlushState.h were previously
we were taking a mutable pointer to the view, which should
at least be a const pointer and was making us do funky things
in some of the calling code. But I decided to go all the way
and do a const ref instead which is The Way It Should Be (tm).

Change-Id: I399d102e8b5e0a5059168cc450ae66f12ad47e13
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/336451
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Adlai Holler <adlai@google.com>
diff --git a/src/gpu/ops/GrMeshDrawOp.cpp b/src/gpu/ops/GrMeshDrawOp.cpp
index d09fa6a..05c3848 100644
--- a/src/gpu/ops/GrMeshDrawOp.cpp
+++ b/src/gpu/ops/GrMeshDrawOp.cpp
@@ -28,7 +28,7 @@
 // This onPrepareDraws implementation assumes the derived Op only has a single programInfo -
 // which is the majority of the cases.
 void GrMeshDrawOp::onPrePrepareDraws(GrRecordingContext* context,
-                                     const GrSurfaceProxyView* writeView,
+                                     const GrSurfaceProxyView& writeView,
                                      GrAppliedClip* clip,
                                      const GrXferProcessor::DstProxyView& dstProxyView,
                                      GrXferBarrierFlags renderPassXferBarriers) {