Called on the UI thread to allow configuration of audio stream parameters. Return true (1) to proceed with audio stream capture, or false (0) to cancel it. All members of |params| can optionally be configured here, but they are also pre-filled with some sensible defaults.
Called on a browser audio capture thread when the browser starts streaming audio. OnAudioStreamStopped will always be called after OnAudioStreamStarted; both functions may be called multiple times for the
Base structure.