Update to GrBackendTexutreImageGenerator to support lazy texture proxies

Bug: skia:
Change-Id: I7cce869894e274250f49328550a0ae2d8e04de74
Reviewed-on: https://skia-review.googlesource.com/95022
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
5 files changed