MailboxSharedGpuContextTest.MailboxCaching always fails for me for the first try and succeeds when retried.

https://chromium-review.googlesource.com/c/chromium/src/+/602679 may be the root cause.

Retrying 1 test (retry #1)
[2193/2193] MailboxSharedGpuContextTest.MailboxCaching (2 ms)
SUCCESS: all tests passed.