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/tools/debugger/SkDebugCanvas.cpp b/tools/debugger/SkDebugCanvas.cpp
index 74e65da..ee3427d 100644
--- a/tools/debugger/SkDebugCanvas.cpp
+++ b/tools/debugger/SkDebugCanvas.cpp
@@ -349,7 +349,7 @@
         // get the render target of the top device so we can ignore batches drawn offscreen
         SkBaseDevice* bd = canvas->getDevice_just_for_deprecated_compatibility_testing();
         SkGpuDevice* gbd = reinterpret_cast<SkGpuDevice*>(bd);
-        uint32_t rtID = gbd->accessDrawContext()->accessRenderTarget()->uniqueID();
+        uint32_t rtID = gbd->accessRenderTargetContext()->accessRenderTarget()->uniqueID();
 
         // get the bounding boxes to draw
         SkTArray<GrAuditTrail::BatchInfo> childrenBounds;