GitLab

If feature flags has changed drivefs may need a restart before it's able
to serve requests. In this case mounting will fail. Make browser handle
this situation by retrying after some time.

BUG=chromium:845390,chromium:845388

Change-Id: I0d4cdcf0e981b0966a23d91d3dc6fd30a32fb927
Reviewed-on: https://chromium-review.googlesource.com/1139943Reviewed-by: Sam McNally <sammc@chromium.org>
Commit-Queue: Sergei Datsenko <dats@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575585}