Bug 1534692 - Part 8: In setIdentityProvider, fall back to the target peer identity if a peerIdentity is not passed. r=jib

Differential Revision: https://phabricator.services.mozilla.com/D24793

--HG--
extra : moz-landing-system : lando

dom/media/PeerConnection.jsm

@@ -1053,6 +1053,7 @@ class RTCPeerConnection {
   setIdentityProvider(provider,
                       {protocol, usernameHint, peerIdentity} = {}) {
     this._checkClosed();
+    peerIdentity = peerIdentity || this._impl.peerIdentity;
     this._localIdp.setIdentityProvider(provider,
                                        protocol, usernameHint, peerIdentity);
   }