Creates a static function on SkImage which converts the SkImage to a
GrBackendTexture. The texture is unowned by Skia, and must be deleted
by the caller. Allows for a no-copy / no-conversion fast path if the
provided image is unowned (unique()) and texture backed.
Change-Id: I8a48f9cc39de792725cd72057d98cd1c4594daab
Reviewed-on: https://skia-review.googlesource.com/52440
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Eric Karl <ericrk@chromium.org>
914a36b248