Clean up test drawContext usage

gm/yuvtorgbeffect.cpp

Index: gm/yuvtorgbeffect.cpp
diff --git a/gm/yuvtorgbeffect.cpp b/gm/yuvtorgbeffect.cpp
index 09c61765fbc0bacaceb6ca1c58cefa5ecc2d4584..40a2f03f27e223f50ed04541b6e9e9f9d9165311 100644
--- a/gm/yuvtorgbeffect.cpp
+++ b/gm/yuvtorgbeffect.cpp
@@ -69,18 +69,14 @@ protected:
     }
 
     void onDraw(SkCanvas* canvas) override {
-        GrRenderTarget* rt = canvas->internal_private_accessTopLayerRenderTarget();
-        if (nullptr == rt) {
-            return;
-        }
-        GrContext* context = rt->getContext();
-        if (nullptr == context) {
+        GrDrawContext* drawContext = canvas->internal_private_accessTopLayerDrawContext();
+        if (!drawContext) {
             skiagm::GM::DrawGpuOnlyMessage(canvas);
-            return;
+            return;        
         }
 
-        sk_sp<GrDrawContext> drawContext(context->drawContext(sk_ref_sp(rt)));
-        if (!drawContext) {
+        GrContext* context = canvas->getGrContext();
+        if (!context) {
             return;
         }
 
@@ -126,7 +122,7 @@ protected:
                 if (fp) {
                     SkMatrix viewMatrix;
                     viewMatrix.setTranslate(x, y);
-                    pipelineBuilder.setRenderTarget(rt);
+                    pipelineBuilder.setRenderTarget(drawContext->accessRenderTarget());
                     pipelineBuilder.addColorFragmentProcessor(fp);
                     SkAutoTUnref<GrDrawBatch> batch(
                             GrRectBatchFactory::CreateNonAAFill(GrColor_WHITE, viewMatrix,