Better handle context-loss in MakeBackendTextureFromSkImage

In context-loss situations, SkImage::getTexture may return nullptr,
even if SkImage::isTextureBacked() is true. Handle these cases
without crashing.

R=bsalomon@google.com

Bug: 803796
Change-Id: Ia877124160fb1893af08f839e43e3ee83c1b93ff
Reviewed-on: https://skia-review.googlesource.com/97341
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
1 file changed