use SkArenaAlloc for combineIfPossible

Now that GrOps no longer needs a GrMemoryPool to be
deleted, just pass down the the SkArenaAlloc instead
of both the GrMemoryPool and SkArenaAlloc.

The alloc is only used for two ops, but we pass it
to all the ops most of which don't use it.

Change-Id: I873efcdfe44b446f2ac5089ea8425dff257e318c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/330118
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Herb Derby <herb@google.com>
diff --git a/src/gpu/ops/GrStrokeRectOp.cpp b/src/gpu/ops/GrStrokeRectOp.cpp
index 2dc2097..1186e15 100644
--- a/src/gpu/ops/GrStrokeRectOp.cpp
+++ b/src/gpu/ops/GrStrokeRectOp.cpp
@@ -480,7 +480,7 @@
     const SkMatrix& viewMatrix() const { return fViewMatrix; }
     bool miterStroke() const { return fMiterStroke; }
 
-    CombineResult onCombineIfPossible(GrOp* t, GrRecordingContext::Arenas*, const GrCaps&) override;
+    CombineResult onCombineIfPossible(GrOp* t, SkArenaAlloc*, const GrCaps&) override;
 
     void generateAAStrokeRectGeometry(GrVertexWriter& vertices,
                                       const SkPMColor4f& color,
@@ -692,8 +692,8 @@
     }
 }
 
-GrOp::CombineResult AAStrokeRectOp::onCombineIfPossible(GrOp* t, GrRecordingContext::Arenas*,
-                                                        const GrCaps& caps) {
+GrOp::CombineResult AAStrokeRectOp::onCombineIfPossible(GrOp* t, SkArenaAlloc*, const GrCaps& caps)
+{
     AAStrokeRectOp* that = t->cast<AAStrokeRectOp>();
 
     if (!fHelper.isCompatible(that->fHelper, caps, this->bounds(), that->bounds())) {