--- a/dom/webidl/RTCPeerConnection.webidl
+++ b/dom/webidl/RTCPeerConnection.webidl
@@ -2,17 +2,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/.
  *
  * The origin of this IDL file is
  * http://w3c.github.io/webrtc-pc/#interface-definition
  */
 
-callback RTCSessionDescriptionCallback = void (RTCSessionDescription sdp);
+callback RTCSessionDescriptionCallback = void (RTCSessionDescriptionInit description);
 callback RTCPeerConnectionErrorCallback = void (DOMError error);
 callback VoidFunction = void ();
 callback RTCStatsCallback = void (RTCStatsReport report);
 
 enum RTCSignalingState {
     "stable",
     "have-local-offer",
     "have-remote-offer",
@@ -77,20 +77,20 @@ interface RTCPeerConnection : EventTarge
   static Promise<RTCCertificate> generateCertificate (AlgorithmIdentifier keygenAlgorithm);
 
   [Pref="media.peerconnection.identity.enabled"]
   void setIdentityProvider (DOMString provider,
                             optional DOMString protocol,
                             optional DOMString username);
   [Pref="media.peerconnection.identity.enabled"]
   Promise<DOMString> getIdentityAssertion();
-  Promise<RTCSessionDescription> createOffer (optional RTCOfferOptions options);
-  Promise<RTCSessionDescription> createAnswer (optional RTCAnswerOptions options);
-  Promise<void> setLocalDescription (RTCSessionDescription description);
-  Promise<void> setRemoteDescription (RTCSessionDescription description);
+  Promise<RTCSessionDescriptionInit> createOffer (optional RTCOfferOptions options);
+  Promise<RTCSessionDescriptionInit> createAnswer (optional RTCAnswerOptions options);
+  Promise<void> setLocalDescription (RTCSessionDescriptionInit description);
+  Promise<void> setRemoteDescription (RTCSessionDescriptionInit description);
   readonly attribute RTCSessionDescription? localDescription;
   readonly attribute RTCSessionDescription? remoteDescription;
   readonly attribute RTCSignalingState signalingState;
   Promise<void> addIceCandidate ((RTCIceCandidateInit or RTCIceCandidate)? candidate);
   readonly attribute boolean? canTrickleIceCandidates;
   readonly attribute RTCIceGatheringState iceGatheringState;
   readonly attribute RTCIceConnectionState iceConnectionState;
   [Pref="media.peerconnection.identity.enabled"]
@@ -149,20 +149,20 @@ partial interface RTCPeerConnection {
   // Dummy Promise<void> return values avoid "WebIDL.WebIDLError: error:
   // We have overloads with both Promise and non-Promise return types"
 
   Promise<void> createOffer (RTCSessionDescriptionCallback successCallback,
                              RTCPeerConnectionErrorCallback failureCallback,
                              optional RTCOfferOptions options);
   Promise<void> createAnswer (RTCSessionDescriptionCallback successCallback,
                               RTCPeerConnectionErrorCallback failureCallback);
-  Promise<void> setLocalDescription (RTCSessionDescription description,
+  Promise<void> setLocalDescription (RTCSessionDescriptionInit description,
                                      VoidFunction successCallback,
                                      RTCPeerConnectionErrorCallback failureCallback);
-  Promise<void> setRemoteDescription (RTCSessionDescription description,
+  Promise<void> setRemoteDescription (RTCSessionDescriptionInit description,
                                       VoidFunction successCallback,
                                       RTCPeerConnectionErrorCallback failureCallback);
   Promise<void> addIceCandidate (RTCIceCandidate candidate,
                                  VoidFunction successCallback,
                                  RTCPeerConnectionErrorCallback failureCallback);
   Promise<void> getStats (MediaStreamTrack? selector,
                           RTCStatsCallback successCallback,
                           RTCPeerConnectionErrorCallback failureCallback);