Handle abandoned context in localmatrixshader GM

Change-Id: If73cb25307ee1607470a75789183cdafec28e03a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/536477
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Herb Derby <herb@google.com>
1 file changed