GitLab

This patch resolves a few issues with GitilesFileSystem.

BUG=404239
NOTRY=True

Review URL: https://codereview.chromium.org/498503002

Cr-Commit-Position: refs/heads/master@{#291357}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291357 0039d316-1c4b-4281-b951-d872f2087c98