Add explicit abandoned flag to the GrProxyProvider

In the DDL world it is valid for the GrProxyProvider to not have a
GrResourceProvider so we need a separate marker for abandonment.

Change-Id: Iae18a25226d35e1152a902e17a8091e0058695f3
Reviewed-on: https://skia-review.googlesource.com/97220
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
2 files changed