If you were creating a new OWNERS file that only had per-file owners
in it (and no catch-all owners for the whole directory), then we
would not look for suggested owners in parent directories, and end up
suggesting nothing. See https://chromiumcodereview.appspot.com/11555036/
for the CL that revealed this.

Also, the unit tests were incorrectly using absolute paths in some cases,
making the code less predictable; I've fixed the unit tests and added
a check for this into owners.py (real changes never used absolute paths,
just paths relative to the checkout root).

R=maruel@chromium.org


Review URL: https://chromiumcodereview.appspot.com/11569018

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@173000 0039d316-1c4b-4281-b951-d872f2087c98