Add checks for failed SkImageInfo2GrPixelConfig calls

Bug: skia:7645
Change-Id: I32b9326fb43490ef6a7a99527243b68d89184ae1
Reviewed-on: https://skia-review.googlesource.com/109083
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
11 files changed