GitLab

This code was previously in
https://chrome-internal.googlesource.com/chrome-app-installer.git

We're moving it to chromium with the goal of having it
eventually built as part of Chrome releases.

The third_party code is used to extract the tags added
by dl.google.com. Omaha uses this mechanism to tag their
meta-installers.

BUG=341353

Review URL: https://codereview.chromium.org/423293004

Cr-Commit-Position: refs/heads/master@{#301492}