An audio track with a level controller with the correct initialization value can be created by a combination of PeerConnectionFactory::CreateAudioTrack(..., audio_source) and either audio_source = PeerConnectionFactory::CreateAudioSource(constraints) or audio_source = PeerConnectionFactory::CreateAudioSource(audio_options). NOTRY=True BUG=webrtc:6386 Review-Url: https://codereview.webrtc.org/2408143003 Cr-Commit-Position: refs/heads/master@{#14693}