Almost remove GrContext

This is everything except for literally removing the class.

Change-Id: I2f16caf865d1bcf9c0f267aed73313c0676a73bb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/327222
Commit-Queue: Adlai Holler <adlai@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/samplecode/Sample.cpp b/samplecode/Sample.cpp
index 2a6e6a1..a69de8e 100644
--- a/samplecode/Sample.cpp
+++ b/samplecode/Sample.cpp
@@ -12,7 +12,7 @@
 #if SK_SUPPORT_GPU
 #   include "include/gpu/GrDirectContext.h"
 #else
-class GrContext;
+class GrDirectContext;
 #endif
 
 //////////////////////////////////////////////////////////////////////////////
@@ -49,7 +49,7 @@
         SkAutoCanvasRestore acr(canvas, true);
         this->onDrawContent(canvas);
 #if SK_SUPPORT_GPU
-        // Ensure the GrContext doesn't combine GrDrawOps across draw loops.
+        // Ensure the context doesn't combine GrDrawOps across draw loops.
         if (auto direct = GrAsDirectContext(canvas->recordingContext())) {
             direct->flushAndSubmit();
         }