Fix the way MB invokes the GYP analyzer.

Also fix a previously broken unittest, add a new unittest, and
make sure the unittests and pylint are run as part of the
presubmit checks.

[email protected]
BUG=481692

Review URL: https://codereview.chromium.org/1279093004

Cr-Commit-Position: refs/heads/master@{#342896}
3 files changed