In a parallel marker world the recursion just avoids proper work
stealing.

It is removed in a separate CL to see the impact of recursive marking on
the benchmarks.

Bug: chromium:750084
Change-Id: Id37ae029e386b45c94e5fecbf349b31d2573d5c0
Reviewed-on: https://chromium-review.googlesource.com/625881Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47516}