- Adds a new AudioStatsTest, with better coverage of the same features, based on call_test. - Adds an AudioEndToEndTest utility, which AudioStatsTest and LowBandwidthAudioTest uses. BUG=webrtc:4690 R=kwiberg@webrtc.org Review-Url: https://codereview.webrtc.org/3008273002 . Cr-Commit-Position: refs/heads/master@{#19833}