Moves cc::Surfaces for Videos onto its own thread.

Previously we were running the cc::Surface for Videos project on the media thread.
This was found to cause some smoothness regressions. This CL fixes that by pushing the
work onto its own thread.

TBR=gab@chromium.org

Bug: 866508
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ide12cb6cebc9dea83a7686c09e6688537bf3389a
Reviewed-on: https://chromium-review.googlesource.com/1176879
Commit-Queue: CJ DiMeglio <lethalantidote@chromium.org>
Reviewed-by: Fran├žois Doray <fdoray@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587811}
11 files changed