Rework how backend-specific formats are retrieved from GrBackendFormat.


Change-Id: If1047c477ff3f2cc4aaf19d2e2e838f2dbcb0126
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/233160
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
21 files changed