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/GrOpsTask.cpp b/src/gpu/GrOpsTask.cpp
index fcbc5a4..7c6b41f 100644
--- a/src/gpu/GrOpsTask.cpp
+++ b/src/gpu/GrOpsTask.cpp
@@ -451,7 +451,7 @@
     for (const auto& chain : fOpChains) {
         if (chain.shouldExecute()) {
             chain.head()->prePrepare(context,
-                                     &fTargets[0],
+                                     this->target(0),
                                      chain.appliedClip(),
                                      chain.dstProxyView(),
                                      fRenderPassXferBarriers);
@@ -481,7 +481,7 @@
             TRACE_EVENT0("skia.gpu", chain.head()->name());
 #endif
             GrOpFlushState::OpArgs opArgs(chain.head(),
-                                          &fTargets[0],
+                                          this->target(0),
                                           chain.appliedClip(),
                                           chain.dstProxyView(),
                                           fRenderPassXferBarriers);
@@ -633,7 +633,7 @@
 #endif
 
         GrOpFlushState::OpArgs opArgs(chain.head(),
-                                      &fTargets[0],
+                                      this->target(0),
                                       chain.appliedClip(),
                                       chain.dstProxyView(),
                                       fRenderPassXferBarriers);