Fix return type of WebRTC createOffer()
@@ -2619,7 +2619,7 @@ RTCPeerConnection.prototype.dispatchEvent = function(evt) {};
* successCallbackOrConstraints
* @param {!RTCPeerConnectionErrorCallback=} errorCallback
* @param {!MediaConstraints=} constraints
- * @return {!Promise<!RTCSessionDescription>|undefined}
+ * @return {!Promise<!RTCSessionDescription>}
*/
RTCPeerConnection.prototype.createOffer = function(successCallbackOrConstraints,
errorCallback, constraints) {};
