Implement disconnect function for GrVkGpu



Apparently this was not added to Vk when it was added to GL. It may be
the cause of a flutter error they are seeing.
Bug: skia:
Change-Id: I4d4e9d1817b308b6c4f01e83f712eb3437e2ad71
Reviewed-on: https://skia-review.googlesource.com/15887
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
2 files changed