sequence_manager: Enable SequenceManager by default in Blink

This patch removes the experiment to enable the SequenceManager on the
renderer main thread (i.e., in Blink). Since the old MessageLoop
implementation was recently removed, the "disabled" arm of this
experiment is now testing a nonsensical configuration
(SequenceManager-on-SequenceManage).

TBR=bcwhite@chromium.org

Bug: 891670
Change-Id: Ic3607bef3de356491a433a6bff50a74331adf821
Reviewed-on: https://chromium-review.googlesource.com/c/1451849
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Sami Kyöstilä <skyostil@chromium.org>
Auto-Submit: Sami Kyöstilä <skyostil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629082}
2 files changed