Allow GrSurfaceProxy-derived classes to use flags when instantiating (take 2)

In some instances proxies must be created that, when instantiated, have no pending IO.

This is split out of:

https://skia-review.googlesource.com/c/8679/ (Add per-Flush callback to GrDrawingManager)

and is a reland of:

https://skia-review.googlesource.com/c/8988/ ( Allow GrSurfaceProxy-derived classes to use flags when instantiating)

Change-Id: I36f52a6d249e762bdfc1f0d7528aba6d4071e492
Reviewed-on: https://skia-review.googlesource.com/9070
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
14 files changed