The previous manual way of triggering the deferred callbacks was very
error-prone, and this was also forgotten at a few places.
We can do better.
Using the RAII programming idiom, the callbacks are now ensured to be
called before returning from public methods.
Also added additional debug checks to ensure that there is a
ScopedDeferrer active whenever callbacks are deferred.
Bug: webrtc:13217
Change-Id: I16a8343b52c00fb30acb018d3846acd0a64318e0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/233242
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35117}
