Specifying the audio buffer size

Some applications involve listening to audio for a potentially extended
period of time (with user consent, of course), and are not particularly
latency-sensitive. An example would be the "Ok Google" hotwording available
on the Chrome new tab page, or other types of continuous speech
recognition. For these applications, a typical low-latency audio
configuration can lead to excessive power usage. I've measured 20% CPU
usage for audio capture in Chrome, for example.

My proposed solution is to offer a way to change the audio buffer size.
This enables a tradeoff between latency and power usage. For example, a
member could be added to MediaTrackConstraintSet
<http://w3c.github.io/mediacapture-main/getusermedia.html#dictionary-mediatrackconstraintset-members>
:

dictionary MediaTrackConstraintSet {
   ...
   audioBufferDurationMs of type ConstrainLong
};

This would be an integer number of milliseconds. Perhaps the name could
mention latency instead (e.g. audioLatencyMs).

How does this simple change sound?

- Charlie