GitLab

ProfileHelperTest.DeleteInactiveProfile and UkmBrowserTest.HistoryDeleteCheck
need the waiting thread to process tasks or they will deadlock.

BUG=749312

Change-Id: I9d18fd55647d32e6e6a33a72be2a0fa8fcd89524
Reviewed-on: https://chromium-review.googlesource.com/988243
Commit-Queue: Robert Liao <robliao@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547819}