I'd like to make sure changes to microtask handling do not break debugging.

R=jarin@chromium.org

Change-Id: I983bd3340261e472b22b0d5b6cded60b64b19d38
Reviewed-on: https://chromium-review.googlesource.com/691715Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48270}