Add GrContextThreadSafeProxy and remove most friends of GrContextThreadSafeProxy

A step towards removing GrCaps from GrContext.h

Also adds operator== to GrContextThreadSafeProxy.

Change-Id: Ic0bae12299dfb0ac8817d9f1c56a1219d6df97d9
Reviewed-on: https://skia-review.googlesource.com/127329
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
6 files changed