Move GrContextOptions to GrContext_Base and make GrContextThreadSafeProxy be derived from GrContext_Base The main thrust of this CL is to bring the GrContextThreadSafeProxy into the fold. Change-Id: I8f457d5b75c69f89beac3a0035b1c05ba5d3b931 Reviewed-on: https://skia-review.googlesource.com/c/188622 Reviewed-by: Brian Salomon <bsalomon@google.com> Commit-Queue: Robert Phillips <robertphillips@google.com>