Revert "Detach op memory pool from recording context"

This reverts commit 6b955167286de1cc0cf215e460389614221903fe.

Reason for revert: breaking some Win10 bots

Original change's description:
> Detach op memory pool from recording context
> 
> This changes GrOpMemoryPool to no longer extend SkRefCnt, and all usages
> either are std::unique_ptr for owners, or GrOpMemoryPool* when ownership
> is held somewhere else. The culmination of this is that DDLs explicitly
> detach the memory pool from the recording context instead of the GrOpsTask
> maintaining a strong ref that preserved the memory somewhat sneakily.
> 
> Change-Id: I33e2caebea70cebe8fd7681207c631feeaf2c703
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/259424
> Commit-Queue: Michael Ludwig <michaelludwig@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>

TBR=bsalomon@google.com,robertphillips@google.com,michaelludwig@google.com

Change-Id: I942ae1e07fdc63d9311f6ee482bd71beca090502
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/259696
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Commit-Queue: Derek Sollenberger <djsollen@google.com>
diff --git a/src/gpu/GrDrawingManager.cpp b/src/gpu/GrDrawingManager.cpp
index 8284a32..083c128 100644
--- a/src/gpu/GrDrawingManager.cpp
+++ b/src/gpu/GrDrawingManager.cpp
@@ -581,7 +581,6 @@
         renderTask->prePrepare(fContext);
     }
 
-    ddl->fOpMemoryPool = fContext->priv().detachOpMemoryPool();
     ddl->fRecordTimeData = fContext->priv().detachRecordTimeAllocator();
 
     fContext->priv().detachProgramInfos(&ddl->fProgramInfos);
@@ -681,7 +680,7 @@
     GrSurfaceProxy* proxy = surfaceView.proxy();
     this->closeRenderTasksForNewRenderTask(proxy);
 
-    sk_sp<GrOpsTask> opsTask(new GrOpsTask(fContext->priv().opMemoryPool(),
+    sk_sp<GrOpsTask> opsTask(new GrOpsTask(fContext->priv().refOpMemoryPool(),
                                            std::move(surfaceView), fContext->priv().auditTrail()));
     SkASSERT(proxy->getLastRenderTask() == opsTask.get());