Use typed promises for UnderlyingSinkBase and its subclasses

Change-Id: I06ee3f9ab7c587a83bc2db069433e7a860449862
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5362619


Commit-Queue: Nate Chapin <japhet@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1271856}