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/texturedomaineffect.cpp b/gm/texturedomaineffect.cpp
index b0d2ece..96f70e0 100644
--- a/gm/texturedomaineffect.cpp
+++ b/gm/texturedomaineffect.cpp
@@ -11,7 +11,7 @@
 
 #if SK_SUPPORT_GPU
 
-#include "GrDrawContextPriv.h"
+#include "GrRenderTargetContextPriv.h"
 #include "GrContext.h"
 #include "SkBitmap.h"
 #include "SkGr.h"
@@ -70,8 +70,9 @@
     }
 
     void onDraw(SkCanvas* canvas) override {
-        GrDrawContext* drawContext = canvas->internal_private_accessTopLayerDrawContext();
-        if (!drawContext) {
+        GrRenderTargetContext* renderTargetContext =
+            canvas->internal_private_accessTopLayerRenderTargetContext();
+        if (!renderTargetContext) {
             skiagm::GM::DrawGpuOnlyMessage(canvas);
             return;
         }
@@ -129,7 +130,8 @@
                     SkAutoTUnref<GrDrawBatch> batch(
                             GrRectBatchFactory::CreateNonAAFill(GrColor_WHITE, viewMatrix,
                                                                 renderRect, nullptr, nullptr));
-                    drawContext->drawContextPriv().testingOnly_drawBatch(grPaint, batch);
+                    renderTargetContext->renderTargetContextPriv().testingOnly_drawBatch(grPaint,
+                                                                                         batch);
                     x += renderRect.width() + kTestPad;
                 }
                 y += renderRect.height() + kTestPad;