Add new SkImage factory to create from GrBackendTexture with SkColorType

Bug: skia:
Change-Id: I46bdc54b6d9cdacc8f5a06644aa6b110837879f0
Reviewed-on: https://skia-review.googlesource.com/84342
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
20 files changed