Update SkSurface_Gpu::Valid to take a backend format

This is pulled out of:

https://skia-review.googlesource.com/c/skia/+/222781 (Add bridge between GrContext::createBackendTexture and SkSurface::MakeFromBackendTexture)

Change-Id: I0c26bba2592a6e6fe759b49de83f994b05d862a2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/223698
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
21 files changed