SkImage::isValid

Lets clients know if an image is drawable to a particular GrContext
(or to CPU). Checks for abandoned GrContexts beneath GPU backed
images, as well as context mis-match.

Bug: skia:
Change-Id: Ibe88c7ce8091f965c14f6023a3597be4b70c3f99
Reviewed-on: https://skia-review.googlesource.com/15801
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
9 files changed