Update TODO for cleaning up DownloadGerritHooks.
Update TODO for cleaning up DownloadGerritHooks.

TBR=phajdan.jr@chromium.org,andybons@chromium.org
BUG=579176

Review URL: https://codereview.chromium.org/1762343002

git-svn-id: fd409f4bdeea2bb50a5d34bb4d4bfc2046a5a3dd@299110 0039d316-1c4b-4281-b951-d872f2087c98

primiano/depot_tools,primiano/depot_tools,primiano/depot_tools,CoherentLabs/depot_tools,CoherentLabs/depot_tools