Remove usage of ScopedTaskScheduler from PipelineIntegrationTestBase.

ScopedTaskScheduler is deprecated.

Bug: 708584
Change-Id: I148560146aa121d8e83fc416b1f86e35934d9054
Reviewed-on: https://chromium-review.googlesource.com/586915
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Francois Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490817}
3 files changed