[graphite] Test that failed dst copies don't cause a crash

This adds a test which would segfault if not for review.skia.org/755577
and review.skia.org/764417.

Bug: chromium:1489392
Change-Id: Iaa83005f0a46522e754de536a86ed912a6e84061
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/766600
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: James Godfrey-Kittle <jamesgk@google.com>
2 files changed