GitLab

Add a completionBlock parameter to ClearBrowsingDataCommand and
use it to wait for the completion of the browsing data removal
in BrowserStateDataRemover.

This allow removing the circular dependency between i/c/b/signin
and i/c/b/browsing_data and to simplify code.

Bug: none
Change-Id: I6ee62201dd321a453be8d7d6d588a8e713735d5f
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Reviewed-on: https://chromium-review.googlesource.com/916607
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537296}