This starts to beef up the capabilities of the GrImageContext in preparation for its future responsibilities (i.e., creating promise images w/o a recordingContext).
Note that the proxyProvider still has different behavior if it has a full context vs. a reduced context. I intend to just let this behavior remain as is.
Change-Id: Idb9d99a548ef928fc1b9dc1e5a34f74343bb0b4b
Reviewed-on: https://skia-review.googlesource.com/c/189490
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
a41c6858da