Clean up test drawContext usage

gm/constcolorprocessor.cpp

Index: gm/constcolorprocessor.cpp
diff --git a/gm/constcolorprocessor.cpp b/gm/constcolorprocessor.cpp
index cfc03398f60af7241ccdb2e527367776eead0f07..4e0e68d2cbd89d6f380db2cb1bbd3e1192229599 100644
--- a/gm/constcolorprocessor.cpp
+++ b/gm/constcolorprocessor.cpp
@@ -47,18 +47,14 @@ 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;
         }
 
-        sk_sp<GrDrawContext> drawContext(context->drawContext(sk_ref_sp(rt)));
-        if (!drawContext) {
+        GrContext* context = canvas->getGrContext();
+        if (!context) {
             return;
         }
 
@@ -112,7 +108,9 @@ protected:
                     SkAutoTUnref<GrFragmentProcessor> fp(GrConstColorProcessor::Create(color, mode));
 
                     GrClip clip;
-                    GrPipelineBuilder pipelineBuilder(grPaint, rt, clip);
+                    GrPipelineBuilder pipelineBuilder(grPaint,
+                                                      drawContext->accessRenderTarget(),
+                                                      clip);
                     pipelineBuilder.addColorFragmentProcessor(fp);
 
                     SkAutoTUnref<GrDrawBatch> batch(