The v8 waterfall currently doesn't run MIPS tests in the debug configuration,
so although there are tests that would have found them, they currently are
not running in the standard CI setup. A bug has been fixed to add the debug
configuration of MIPS & MIPS64, too.

Review-Url: https://codereview.chromium.org/2654263002
Cr-Commit-Position: refs/heads/master@{#42727}