In the current form, SequencedTaskRunner::DeleteSoon() may lead to memory leaks during shutdown, for the case where it returns |true|, because there's no guarantee about whether the task will run or not.

Some callers have worked this around on the calling site, e.g.: https://cs.chromium.org/chromium/src/base/threading/post_task_and_reply_impl.cc?l=57&rcl=789766a26dc5f1009c20450489ab6ea1841c7495

There's also a related TODO(akalin) in SequencedTaskRunner to "Get rid of the boolean return value for the methods".

My personal proposal would be to introduce more specifics functions like:
1. DeleteSoonOrLeak.
2. DeleteEventuallyInAnySequence

thakis@: does this make sense?