Allow draw_to_canvas to pass through the GrDirectContext.

Some GM slides behave differently when a GrDirectContext is passed (e.g.
the CTMPathEffectGM disables itself when the GrDirectContext is non-null
because it asserts when run on GPU).

Change-Id: Ida18f191474f94426c6077d3a5de659e739056a4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/430476
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed