GitLab

- Ported Omaha 3's ExtraArgsParser into chrome/updater.
- (At Sorin's request) Renamed ExtraArgs to something else (currently TagArgs, but I'm open to renaming it or any other item)
- Ported the Omaha 3 ExtraArgsParser tests

Change-Id: Ief76020716ae35fff26bacd19357847651acad5a
Bug: 1050738
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2081332
Commit-Queue: Michael Tang <tangm@microsoft.com>
Reviewed-by: Sorin Jianu <sorin@chromium.org>
Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756449}