This method could be called on pause and will do stepInto next scheduled callback if any will happen until next break.
First implementation support only callbacks chained by Promise.prototype.then.
BUG=chromium:432469
R=yangguo@chromium.org,dgozman@chromium.org
Review-Url: https://codereview.chromium.org/2723273002
Cr-Commit-Position: refs/heads/master@{#43616}
