Enable IceGatheringState test

Rewrite test so that it does not hang (create promise before
event that it is waiting for).

Bug: chromium:1115080
Change-Id: Ic445bef22561a1d997b4d3657a76e1b0779a1259
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2367854Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800544}

third_party/blink/web_tests/TestExpectations

@@ -3062,7 +3062,6 @@ virtual/webrtc-wpt-plan-b/external/wpt/webrtc/RTCPeerConnection-restartIce-onneg
 crbug.com/1110833 external/wpt/webrtc/RTCPeerConnection-explicit-rollback-iceGatheringState.html [ Timeout ]
 
 # Tests that start hanging after implementing RTCRtpTransceiver.stop
-crbug.com/1115080 external/wpt/webrtc/RTCPeerConnection-iceGatheringState.html [ Timeout Pass Failure ]
 crbug.com/1115087 external/wpt/webrtc/RTCRtpTransceiver.https.html [ Timeout ]
 
 # See also crbug.com/920100 (sheriff 2019-01-09).

third_party/blink/web_tests/external/wpt/webrtc/RTCPeerConnection-iceGatheringState-expected.txt

-This is a testharness.js-based test.
-PASS Initial iceGatheringState should be new
-PASS iceGatheringState should eventually become complete after setLocalDescription
-PASS setLocalDescription(reoffer) with no new transports should not cause iceGatheringState to change
-PASS setLocalDescription(reoffer) with a new transport should cause iceGatheringState to go to "checking" and then "complete"
-PASS sRD does not cause ICE gathering state changes
-FAIL renegotiation that closes all transports should result in ICE gathering state "new" promise_test: Unhandled rejection with value: object "TypeError: pc1.getTransceivers(...)[0].stop is not a function"
-PASS connection with one data channel should eventually have connected connection state
-Harness: the test ran to completion.
-

third_party/blink/web_tests/external/wpt/webrtc/RTCPeerConnection-iceGatheringState.html

@@ -133,17 +133,21 @@
     await initialOfferAnswerWithIceGatheringStateTransitions(
         pc1, pc2, {offerToReceiveAudio: true});
 
+    const pc1waiter = iceGatheringStateTransitions(pc1, 'new');
+    const pc2waiter = iceGatheringStateTransitions(pc2, 'new');
     pc1.getTransceivers()[0].stop();
     await pc1.setLocalDescription(await pc1.createOffer());
     await pc2.setRemoteDescription(pc1.localDescription);
     await pc2.setLocalDescription(await pc2.createAnswer());
     assert_equals(pc2.getTransceivers().length, 0,
                  'PC2 transceivers should be invisible after negotiation');
-    await iceGatheringStateTransitions(pc2, 'new');
+    assert_equals(pc2.iceGatheringState, 'new');
+    await pc2waiter;
     await pc1.setRemoteDescription(pc2.localDescription);
     assert_equals(pc1.getTransceivers().length, 0,
-                 'PC1 transceivers should be invisible after negotiation');
-    await iceGatheringStateTransitions(pc1, 'new');
+                  'PC1 transceivers should be invisible after negotiation');
+    assert_equals(pc1.iceGatheringState, 'new');
+    await pc1waiter;
   }, 'renegotiation that closes all transports should result in ICE gathering state "new"');
 
   /*