PSA: Spec-compliant audio constraint processing for getUserMedia enabled by default in Chrome 61

[gui...@webrtc.org]

Spec-compliant audio-constraints processing for getUserMedia is enabled by default since Chrome 61.0.3146.0.

This allows developers to take advantage of features such as "ideal" values and atomic constraint-set application. For more details about the standard, see https://w3c.github.io/mediacapture-main/#dom-mediadevices-getusermedia.

We expect that most applications will continue to work without modification, but we advise developers to test their applications with the current Chrome Canary and future beta versions of Chrome 61.

If you have questions or experience any issues, please email gui...@chromium.org or file bugs at https://crbug.com and assign them to gui...@chromium.org.

To use the old constraints-processing algorithm, start Chrome with the following command-line flag:

--enable-features=MediaStreamOldAudioConstraints

[gui...@webrtc.org]

Note that the MediaStreamOldAudioConstraints feature flag is intended only to help diagnose bugs and to provide an easy mechanism to revert to the old algorithm in case the new one turns out to be broken in an unexpected way.

We plan to remove the flag in Chrome 63.