base: Use original MessageLoop backend in performance test

We should re-enable the original MessageLoop backend in the
SequenceManager performance test; otherwise the test will compare the
SequenceManager-backend against itself.

Bug: 891670
Change-Id: I352fd61e7c37b283f8003ff815b7f4f41c2d0b22
Reviewed-on: https://chromium-review.googlesource.com/c/1438997
Auto-Submit: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626525}
3 files changed