Replace direct use of offerToReceiveAudio by generateAudioReceiveOnlyOffer. This allows to use non legacy APIs by default if supported. 
diff --git a/webrtc/RTCPeerConnection-setLocalDescription-rollback.html b/webrtc/RTCPeerConnection-setLocalDescription-rollback.html index 0147b31..630f84f 100644 --- a/webrtc/RTCPeerConnection-setLocalDescription-rollback.html +++ b/webrtc/RTCPeerConnection-setLocalDescription-rollback.html 
@@ -12,6 +12,7 @@    // The following helper functions are called from RTCPeerConnection-helper.js:  // assert_session_desc_similar + // generateAudioReceiveOnlyOffer    /*  4.3.2. Interface Definition @@ -105,7 +106,7 @@  promise_test(t => {  const pc = new RTCPeerConnection();  t.add_cleanup(() => pc.close()); - return pc.createOffer({ offerToReceiveAudio: true }) + return generateAudioReceiveOnlyOffer(pc)  .then(offer =>  pc.setRemoteDescription(offer)  .then(() => pc.createAnswer()))