This way the first scheduler can properly wire them to the effect chain,
as otherwise the second scheduler could schedule them such that they
would be able to read uninitialized memory (once we drop the region
protection in the first scheduler).

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/1908963002

Cr-Commit-Position: refs/heads/master@{#35707}