Fix test failure caused by inappropriate event sequencing.

This is a minimal fix - move the generation of the track (which
causes onnegotiationneeded) to before we set the expectation that
no event will be fired.

Bug: chromium:905563
Change-Id: I879f6eb6130d719d7eaad71fed85044b690f0cb9
Reviewed-on: https://chromium-review.googlesource.com/c/1346030Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609999}

third_party/WebKit/LayoutTests/external/wpt/webrtc/RTCPeerConnection-onnegotiationneeded.html

@@ -164,10 +164,13 @@
    */
   test_never_resolve(t => {
     const pc = new RTCPeerConnection();
-    const negotiated = awaitNegotiation(pc);
+    let negotiated;
 
     return generateAudioReceiveOnlyOffer(pc)
-    .then(offer => pc.setLocalDescription(offer))
+    .then(offer => {
+      pc.setLocalDescription(offer);
+      negotiated = awaitNegotiation(pc);
+    })
     .then(() => negotiated)
     .then(({nextPromise}) => {
       assert_equals(pc.signalingState, 'have-local-offer');

third_party/WebKit/LayoutTests/virtual/webrtc-wpt-unified-plan/external/wpt/webrtc/RTCPeerConnection-onnegotiationneeded-expected.txt

@@ -4,7 +4,7 @@ PASS calling createDataChannel twice should fire negotiationneeded event once
 PASS addTransceiver() should fire negotiationneeded event
 FAIL Calling addTransceiver() twice should fire negotiationneeded event once assert_unreached: Pending promise should never be resolved. Instead it is fulfilled with: [object Object] Reached unreachable code
 FAIL Calling both addTransceiver() and createDataChannel() should fire negotiationneeded event once assert_unreached: Pending promise should never be resolved. Instead it is fulfilled with: [object Object] Reached unreachable code
-FAIL negotiationneeded event should not fire if signaling state is not stable assert_unreached: Pending promise should never be resolved. Instead it is fulfilled with: [object Object] Reached unreachable code
+PASS negotiationneeded event should not fire if signaling state is not stable
 FAIL negotiationneeded event should fire only after signaling state go back to stable assert_unreached: Expect negotiationneeded promise to resolve after pc has set remote answer and go back to stable state Reached unreachable code
 Harness: the test ran to completion.