pt6 - improve RTCDtlsTransport-state.html addIceCandidate calls.

Make these calls more acceptable to Chrome.

Depends on 96662

Differential Revision: https://phabricator.services.mozilla.com/D96774

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1654399
gecko-commit: feab772596ad39e2566f02f07ef56cda60e19231
gecko-reviewers: bwc

webrtc/RTCDtlsTransport-state.html

@@ -93,8 +93,22 @@
   t.add_cleanup(() => pc1.close());
   t.add_cleanup(() => pc2.close());
 
-  pc1.onicecandidate = e => pc2.addIceCandidate(e.candidate);
-  pc2.onicecandidate = e => pc1.addIceCandidate(e.candidate);
+  pc1.onicecandidate = e => {
+    if (e.candidate) {
+      pc2.addIceCandidate({
+        candidate: e.candidate.candidate,
+        sdpMid: e.candidate.sdpMid
+      });
+    }
+  }
+  pc2.onicecandidate = e => {
+    if (e.candidate) {
+      pc1.addIceCandidate({
+        candidate: e.candidate.candidate,
+        sdpMid: e.candidate.sdpMid
+      });
+    }
+  }
 
   pc1.addTransceiver("video");
   pc1.addTransceiver("audio");