[ios] Add wait for testSignInSwitchAccountsAndKeepDataSeparate.

Bug: 989618
Change-Id: Ie826531bc0e891bcea5524cdecdc662692d0e2de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1732350
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683868}
1 file changed