Bug 1534673 - Part 2: Update a couple of mochitests to stop checking track ids. r=jib

Differential Revision: https://phabricator.services.mozilla.com/D23207

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

dom/media/tests/mochitest/test_peerConnection_addtrack_removetrack_events.html

@@ -52,7 +52,6 @@ runNetworkTest(function (options) {
                  "Expected event to be instance of MediaStreamTrackEvent");
               is(trackEvent.type, "addtrack",
                  "Expected addtrack event type");
-              is(test.pcRemote.getWebrtcTrackId(trackEvent.track), newTrack.id, "Expected track in event");
               is(trackEvent.track.readyState, "live",
                  "added track should be live");
             })

dom/media/tests/mochitest/test_peerConnection_constructedStream.html

@@ -49,9 +49,6 @@ runNetworkTest(() => {
 
     is(receivedStream.getTracks().length, sentTracks.length,
        "Should receive same number of tracks as were sent");
-    sentTracks.forEach(t =>
-      ok(receivedStream.getTracks().find(t2 => t.id == test.pcRemote.getWebrtcTrackId(t2)),
-         "The sent track (" + t.id + ") should exist on the receive side"));
   };
 
   test.chain.append([