Fix RTCPeerConnection-transceivers.https.html bug.

This PR accidentally made the "addTrack(0 streams)" test call addTrack()
with a stream, which broke the tests:
#12141

Test restored and all "addTrack/addTransceiver(X streams)" are made to
consistently use "new MediaStream()" the same way.

Bug: 869036
Change-Id: Ieaf0c73a1996aeb2e87e18f2f9065fa1e6fee1e7
Reviewed-on: https://chromium-review.googlesource.com/1155125
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579341}

webrtc/RTCPeerConnection-transceivers.https.html

@@ -321,7 +321,7 @@
 promise_test(async t => {
   const pc1 = createPeerConnectionWithCleanup(t);
   const pc2 = createPeerConnectionWithCleanup(t);
-  const [track, stream] = await createTrackAndStreamWithCleanup(t);
+  const [track] = await createTrackAndStreamWithCleanup(t);
   pc1.addTransceiver(track, {streams:[]});
   const trackEvent = await exchangeOfferAndListenToOntrack(t, pc1, pc2);
   assert_equals(trackEvent.streams.length, 0, 'trackEvent.streams.length == 0');
@@ -330,7 +330,8 @@
 promise_test(async t => {
   const pc1 = createPeerConnectionWithCleanup(t);
   const pc2 = createPeerConnectionWithCleanup(t);
-  const [track, stream] = await createTrackAndStreamWithCleanup(t);
+  const [track] = await createTrackAndStreamWithCleanup(t);
+  const stream = new MediaStream();
   pc1.addTransceiver(track, {streams:[stream]});
   const trackEvent = await exchangeOfferAndListenToOntrack(t, pc1, pc2);
   assert_equals(trackEvent.streams.length, 1, 'trackEvent.streams.length == 1');
@@ -341,7 +342,7 @@
 promise_test(async t => {
   const pc1 = createPeerConnectionWithCleanup(t);
   const pc2 = createPeerConnectionWithCleanup(t);
-  const [track, stream] = await createTrackAndStreamWithCleanup(t);
+  const [track] = await createTrackAndStreamWithCleanup(t);
   const stream0 = new MediaStream();
   const stream1 = new MediaStream();
   pc1.addTransceiver(track, {streams:[stream0, stream1]});
@@ -356,16 +357,17 @@
 promise_test(async t => {
   const pc1 = createPeerConnectionWithCleanup(t);
   const pc2 = createPeerConnectionWithCleanup(t);
-  const [track, stream] = await createTrackAndStreamWithCleanup(t);
-  pc1.addTrack(track, stream);
+  const [track] = await createTrackAndStreamWithCleanup(t);
+  pc1.addTrack(track);
   const trackEvent = await exchangeOfferAndListenToOntrack(t, pc1, pc2);
   assert_equals(trackEvent.streams.length, 0, 'trackEvent.streams.length == 0');
 }, 'addTrack(0 streams): ontrack fires with no stream');
 
 promise_test(async t => {
   const pc1 = createPeerConnectionWithCleanup(t);
   const pc2 = createPeerConnectionWithCleanup(t);
-  const [track, stream] = await createTrackAndStreamWithCleanup(t);
+  const [track] = await createTrackAndStreamWithCleanup(t);
+  const stream = new MediaStream();
   pc1.addTrack(track, stream);
   const trackEvent = await exchangeOfferAndListenToOntrack(t, pc1, pc2);
   assert_equals(trackEvent.streams.length, 1, 'trackEvent.streams.length == 1');
@@ -376,7 +378,7 @@
 promise_test(async t => {
   const pc1 = createPeerConnectionWithCleanup(t);
   const pc2 = createPeerConnectionWithCleanup(t);
-  const [track, stream] = await createTrackAndStreamWithCleanup(t);
+  const [track] = await createTrackAndStreamWithCleanup(t);
   const stream0 = new MediaStream();
   const stream1 = new MediaStream();
   pc1.addTrack(track, stream0, stream1);