Remove GrPendingIOResource

AFAICT these three remaining uses of GrPendingIOResource were just real-ref placeholders (i.e., they just added 1 pending read and then held on to the GrPendingIOResource until object destruction).

Change-Id: Iba6bb199477d846d079999f09794422e240c675a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/235458
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrResourceCache.cpp b/src/gpu/GrResourceCache.cpp
index 4dd0481..0f7deb3 100644
--- a/src/gpu/GrResourceCache.cpp
+++ b/src/gpu/GrResourceCache.cpp
@@ -862,6 +862,9 @@
         void update(GrGpuResource* resource) {
             fBytes += resource->gpuMemorySize();
 
+            // No resource should ever have pendingIO any more
+            SkASSERT(!resource->internalHasPendingIO());
+
             if (!resource->resourcePriv().isPurgeable()) {
                 ++fLocked;
             }