This CL mainly just:
stores the GrContextOptions in GrContextThreadSafeProxy (so they can be passed on to a stubbed out GrContext)
adds a method to create a stubbed out GrContext that has a GrStubGpu
- the stubbed out GrContext isn't quite ready for prime time yet
Change-Id: I31be6763640e406c5963e6f0714489ac358339e4
Reviewed-on: https://skia-review.googlesource.com/79601
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>