Remove use of SkCanvas::getGrContext which is going away

We already have the GrDirectContext available, so just use that.

Change-Id: I49436e7a8fefc0cc3bdd9e6425bd730c4a897e03
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410539
Auto-Submit: Adlai Holler <adlai@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Alexander Cooper <alcooper@chromium.org>
Commit-Queue: Adlai Holler <adlai@google.com>
Cr-Commit-Position: refs/heads/master@{#807415}

chrome/browser/vr/cmd_buffer_surface_provider.cc

@@ -49,7 +49,7 @@ GLuint CmdBufferSurfaceProvider::FlushSurface(SkSurface* surface,
   DCHECK(result);
   GLuint texture_id = info.fID;
   DCHECK_NE(texture_id, 0u);
-  surface->getCanvas()->getGrContext()->resetContext();
+  gr_context_->resetContext();
   glBindFramebuffer(GL_FRAMEBUFFER, main_fbo_);
 
   return texture_id;

chrome/browser/vr/native_gl_surface_provider.cc

@@ -52,7 +52,7 @@ GLuint NativeGlSurfaceProvider::FlushSurface(SkSurface* surface,
   DCHECK(result);
   GLuint texture_id = info.fID;
   DCHECK_NE(texture_id, 0u);
-  surface->getCanvas()->getGrContext()->resetContext();
+  gr_context_->resetContext();
   glBindFramebufferEXT(GL_FRAMEBUFFER, main_fbo_);
 
   return texture_id;