Initialize BackgroundServiceManager at the test case level in views mus tests.

It was previously initialized at the test suite level, before
TaskScheduler initialization. That prevented adding calls to
base/task_scheduler/post_task.h in the BackgroundServiceManager
initialization code (see
https://chromium-review.googlesource.com/c/chromium/src/+/850736).

Bug: 667892
Change-Id: I94d1ded90d4cfdb11422813014ce9e13f4260c6e
Reviewed-on: https://chromium-review.googlesource.com/861201
Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529009}
3 files changed