GitLab

Uses the ExploreSitesFetcher to get the latest catalog from the network,
and upload it into our database for use on next run of ExploreSites.

Bug: 889104
Change-Id: I2d414e6cea59271252fa735bd59191706dead377
Reviewed-on: https://chromium-review.googlesource.com/1243673
Commit-Queue: Peter Williamson <petewil@chromium.org>
Reviewed-by: Justin DeWitt <dewittj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594589}