GitLab

Delete code related to the github file system since it's not been used
for years. Also delete some other obsolete code.

BUG=820606, 1105728


Change-Id: Ia4b4e851ddd3b5ca640ca892bf27e3e934c96369
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2311897
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791030}