Reduce reliance on the SkImage_Gpu's GrContext pointer

The SkImages aren't guaranteed to have a full fledged GrContext (e.g., if they are promise images created outside of a DDL recorder). This CL starts the process if lessening Skia's reliance on what ever the SkImage has cached.

Change-Id: I0181d09417e1ea2ced7706a722e2815f3ceee870
Reviewed-on: https://skia-review.googlesource.com/c/182974
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
12 files changed