Implement RequestUpdatedSharePath in SmbService

- Logic of time throttling HostDiscovery is added to
  RequestUpdatedSharePath.
- HostDiscovery will only run if the time interval has expired since the
  last call to HostDiscovery.
  Currently set to one minute.
- Add OnHostsDiscoveredForUpdateSharePath as a closure for HostDiscovery.

Bug: 922273
Test: compiles
Change-Id: I7b346c1f2bdfe2b87c028e09436465498a0ac7f1
Reviewed-on: https://chromium-review.googlesource.com/c/1445237
Commit-Queue: jimmy gong <jimmyxgong@chromium.org>
Auto-Submit: jimmy gong <jimmyxgong@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630890}
2 files changed