Reduce GrOnFlushResourceProvider's functionality

The main goal of this CL was to remove GrOnFlushResourceProvider::makeSurfaceDrawContext (which was only being used in the OnFlushCallbackTest) to allow simpler modifications to GrSurfaceDrawContext. It looks like there was a lot more unused stuff here though.

Bug: skia:11837
Change-Id: Idbc4001c58a4e8456bffcf1bac32150f2452fb56
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/430043
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrDrawingManager.cpp b/src/gpu/GrDrawingManager.cpp
index 77e754b..bc981e3 100644
--- a/src/gpu/GrDrawingManager.cpp
+++ b/src/gpu/GrDrawingManager.cpp
@@ -23,6 +23,7 @@
 #include "src/gpu/GrGpu.h"
 #include "src/gpu/GrMemoryPool.h"
 #include "src/gpu/GrOnFlushResourceProvider.h"
+#include "src/gpu/GrOpFlushState.h"
 #include "src/gpu/GrRecordingContextPriv.h"
 #include "src/gpu/GrRenderTargetProxy.h"
 #include "src/gpu/GrRenderTask.h"