GitLab

Updates expand_owners_unittest.py to work even if the
checkout does not begin with a 'chromium' dir.

Note: This does not fix the issue that makes this test
fail on bots yet and so doesn't re-add it to the list of
tests ran by metrics_python_tests.py. This is a slightly
different issue, where on bots, there isn't even a 'src'
directory, which trips up other assumptions in the test.

Bug: 1126653
Change-Id: I0f345f3efa3a54b4f7ba08106fd6d08ffbc5345b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2505573
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Auto-Submit: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/master@{#821875}