This reduces spam in our unit tests. Speeds up test execution.

Bug: angleproject:3162
Change-Id: I286a18b3ce862c4e4155076b2ee3f93c9db2eb33
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2447041
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>