Rename GrDrawContext to GrRenderTargetContext

This is in preparation for GrTextureContext and GrSurfaceContext

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4030

Change-Id: Ie58c93052e68f3f1f5fe8d15d63760de274a6fbd
Reviewed-on: https://skia-review.googlesource.com/4030
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/gm/rrects.cpp b/gm/rrects.cpp
index 1f47f77..6e0995d 100644
--- a/gm/rrects.cpp
+++ b/gm/rrects.cpp
@@ -8,7 +8,7 @@
 #include "gm.h"
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
-#include "GrDrawContextPriv.h"
+#include "GrRenderTargetContextPriv.h"
 #include "batches/GrDrawBatch.h"
 #include "batches/GrRectBatchFactory.h"
 #include "effects/GrRRectEffect.h"
@@ -62,8 +62,9 @@
     SkISize onISize() override { return SkISize::Make(kImageWidth, kImageHeight); }
 
     void onDraw(SkCanvas* canvas) override {
-        GrDrawContext* drawContext = canvas->internal_private_accessTopLayerDrawContext();
-        if (kEffect_Type == fType && !drawContext) {
+        GrRenderTargetContext* renderTargetContext =
+            canvas->internal_private_accessTopLayerRenderTargetContext();
+        if (kEffect_Type == fType && !renderTargetContext) {
             skiagm::GM::DrawGpuOnlyMessage(canvas);
             return;
         }
@@ -117,7 +118,8 @@
                             SkAutoTUnref<GrDrawBatch> batch(
                                     GrRectBatchFactory::CreateNonAAFill(0xff000000, SkMatrix::I(),
                                                                         bounds, nullptr, nullptr));
-                            drawContext->drawContextPriv().testingOnly_drawBatch(grPaint, batch);
+                            renderTargetContext->renderTargetContextPriv().testingOnly_drawBatch(
+                                                                                    grPaint, batch);
                         } else {
                             drew = false;
                         }