Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 715 insertions, 0 deletions

diff --git a/testing/web-platform/tests/webrtc/RTCPeerConnection-helper.js b/testing/web-platform/tests/webrtc/RTCPeerConnection-helper.js
new file mode 100644
index 0000000000..ac435279bd
--- /dev/null
+++ b/testing/web-platform/tests/webrtc/RTCPeerConnection-helper.js
@@ -0,0 +1,715 @@
+'use strict'
+
+/*
+ *  Helper Methods for testing the following methods in RTCPeerConnection:
+ *    createOffer
+ *    createAnswer
+ *    setLocalDescription
+ *    setRemoteDescription
+ *
+ *  This file offers the following features:
+ *    SDP similarity comparison
+ *    Generating offer/answer using anonymous peer connection
+ *    Test signalingstatechange event
+ *    Test promise that never resolve
+ */
+
+const audioLineRegex = /\r\nm=audio.+\r\n/g;
+const videoLineRegex = /\r\nm=video.+\r\n/g;
+const applicationLineRegex = /\r\nm=application.+\r\n/g;
+
+function countLine(sdp, regex) {
+  const matches = sdp.match(regex);
+  if(matches === null) {
+    return 0;
+  } else {
+    return matches.length;
+  }
+}
+
+function countAudioLine(sdp) {
+  return countLine(sdp, audioLineRegex);
+}
+
+function countVideoLine(sdp) {
+  return countLine(sdp, videoLineRegex);
+}
+
+function countApplicationLine(sdp) {
+  return countLine(sdp, applicationLineRegex);
+}
+
+function similarMediaDescriptions(sdp1, sdp2) {
+  if(sdp1 === sdp2) {
+    return true;
+  } else if(
+    countAudioLine(sdp1) !== countAudioLine(sdp2) ||
+    countVideoLine(sdp1) !== countVideoLine(sdp2) ||
+    countApplicationLine(sdp1) !== countApplicationLine(sdp2))
+  {
+    return false;
+  } else {
+    return true;
+  }
+}
+
+// Assert that given object is either an
+// RTCSessionDescription or RTCSessionDescriptionInit
+function assert_is_session_description(sessionDesc) {
+  if(sessionDesc instanceof RTCSessionDescription) {
+    return;
+  }
+
+  assert_not_equals(sessionDesc, undefined,
+    'Expect session description to be defined');
+
+  assert_true(typeof(sessionDesc) === 'object',
+    'Expect sessionDescription to be either a RTCSessionDescription or an object');
+
+  assert_true(typeof(sessionDesc.type) === 'string',
+    'Expect sessionDescription.type to be a string');
+
+  assert_true(typeof(sessionDesc.sdp) === 'string',
+    'Expect sessionDescription.sdp to be a string');
+}
+
+
+// We can't do string comparison to the SDP content,
+// because RTCPeerConnection may return SDP that is
+// slightly modified or reordered from what is given
+// to it due to ICE candidate events or serialization.
+// Instead, we create SDP with different number of media
+// lines, and if the SDP strings are not the same, we
+// simply count the media description lines and if they
+// are the same, we assume it is the same.
+function isSimilarSessionDescription(sessionDesc1, sessionDesc2) {
+  assert_is_session_description(sessionDesc1);
+  assert_is_session_description(sessionDesc2);
+
+  if(sessionDesc1.type !== sessionDesc2.type) {
+    return false;
+  } else {
+    return similarMediaDescriptions(sessionDesc1.sdp, sessionDesc2.sdp);
+  }
+}
+
+function assert_session_desc_similar(sessionDesc1, sessionDesc2) {
+  assert_true(isSimilarSessionDescription(sessionDesc1, sessionDesc2),
+    'Expect both session descriptions to have the same count of media lines');
+}
+
+function assert_session_desc_not_similar(sessionDesc1, sessionDesc2) {
+  assert_false(isSimilarSessionDescription(sessionDesc1, sessionDesc2),
+    'Expect both session descriptions to have different count of media lines');
+}
+
+async function generateDataChannelOffer(pc) {
+  pc.createDataChannel('test');
+  const offer = await pc.createOffer();
+  assert_equals(countApplicationLine(offer.sdp), 1, 'Expect m=application line to be present in generated SDP');
+  return offer;
+}
+
+async function generateAudioReceiveOnlyOffer(pc)
+{
+    try {
+        pc.addTransceiver('audio', { direction: 'recvonly' });
+        return pc.createOffer();
+    } catch(e) {
+        return pc.createOffer({ offerToReceiveAudio: true });
+    }
+}
+
+async function generateVideoReceiveOnlyOffer(pc)
+{
+    try {
+        pc.addTransceiver('video', { direction: 'recvonly' });
+        return pc.createOffer();
+    } catch(e) {
+        return pc.createOffer({ offerToReceiveVideo: true });
+    }
+}
+
+// Helper function to generate answer based on given offer using a freshly
+// created RTCPeerConnection object
+async function generateAnswer(offer) {
+  const pc = new RTCPeerConnection();
+  await pc.setRemoteDescription(offer);
+  const answer = await pc.createAnswer();
+  pc.close();
+  return answer;
+}
+
+// Helper function to generate offer using a freshly
+// created RTCPeerConnection object
+async function generateOffer() {
+  const pc = new RTCPeerConnection();
+  const offer = await pc.createOffer();
+  pc.close();
+  return offer;
+}
+
+// Run a test function that return a promise that should
+// never be resolved. For lack of better options,
+// we wait for a time out and pass the test if the
+// promise doesn't resolve within that time.
+function test_never_resolve(testFunc, testName) {
+  async_test(t => {
+    testFunc(t)
+    .then(
+      t.step_func(result => {
+        assert_unreached(`Pending promise should never be resolved. Instead it is fulfilled with: ${result}`);
+      }),
+      t.step_func(err => {
+        assert_unreached(`Pending promise should never be resolved. Instead it is rejected with: ${err}`);
+      }));
+
+    t.step_timeout(t.step_func_done(), 100)
+  }, testName);
+}
+
+// Helper function to exchange ice candidates between
+// two local peer connections
+function exchangeIceCandidates(pc1, pc2) {
+  // private function
+  function doExchange(localPc, remotePc) {
+    localPc.addEventListener('icecandidate', event => {
+      const { candidate } = event;
+
+      // Guard against already closed peerconnection to
+      // avoid unrelated exceptions.
+      if (remotePc.signalingState !== 'closed') {
+        remotePc.addIceCandidate(candidate);
+      }
+    });
+  }
+
+  doExchange(pc1, pc2);
+  doExchange(pc2, pc1);
+}
+
+// Returns a promise that resolves when a |name| event is fired.
+function waitUntilEvent(obj, name) {
+  return new Promise(r => obj.addEventListener(name, r, {once: true}));
+}
+
+// Returns a promise that resolves when the |transport.state| is |state|
+// This should work for RTCSctpTransport, RTCDtlsTransport and RTCIceTransport.
+async function waitForState(transport, state) {
+  while (transport.state != state) {
+    await waitUntilEvent(transport, 'statechange');
+  }
+}
+
+// Returns a promise that resolves when |pc.iceConnectionState| is 'connected'
+// or 'completed'.
+async function listenToIceConnected(pc) {
+  await waitForIceStateChange(pc, ['connected', 'completed']);
+}
+
+// Returns a promise that resolves when |pc.iceConnectionState| is in one of the
+// wanted states.
+async function waitForIceStateChange(pc, wantedStates) {
+  while (!wantedStates.includes(pc.iceConnectionState)) {
+    await waitUntilEvent(pc, 'iceconnectionstatechange');
+  }
+}
+
+// Returns a promise that resolves when |pc.connectionState| is 'connected'.
+async function listenToConnected(pc) {
+  while (pc.connectionState != 'connected') {
+    await waitUntilEvent(pc, 'connectionstatechange');
+  }
+}
+
+// Returns a promise that resolves when |pc.connectionState| is in one of the
+// wanted states.
+async function waitForConnectionStateChange(pc, wantedStates) {
+  while (!wantedStates.includes(pc.connectionState)) {
+    await waitUntilEvent(pc, 'connectionstatechange');
+  }
+}
+
+async function waitForIceGatheringState(pc, wantedStates) {
+  while (!wantedStates.includes(pc.iceGatheringState)) {
+    await waitUntilEvent(pc, 'icegatheringstatechange');
+  }
+}
+
+// Resolves when RTP packets have been received.
+async function listenForSSRCs(t, receiver) {
+  while (true) {
+    const ssrcs = receiver.getSynchronizationSources();
+    if (Array.isArray(ssrcs) && ssrcs.length > 0) {
+      return ssrcs;
+    }
+    await new Promise(r => t.step_timeout(r, 0));
+  }
+}
+
+// Helper function to create a pair of connected data channels.
+// On success the promise resolves to an array with two data channels.
+// It does the heavy lifting of performing signaling handshake,
+// ICE candidate exchange, and waiting for data channel at two
+// end points to open. Can do both negotiated and non-negotiated setup.
+async function createDataChannelPair(t, options,
+                                     pc1 = createPeerConnectionWithCleanup(t),
+                                     pc2 = createPeerConnectionWithCleanup(t)) {
+  let pair = [], bothOpen;
+  try {
+    if (options.negotiated) {
+      pair = [pc1, pc2].map(pc => pc.createDataChannel('', options));
+      bothOpen = Promise.all(pair.map(dc => new Promise((r, e) => {
+        dc.onopen = r;
+        dc.onerror = ({error}) => e(error);
+      })));
+    } else {
+      pair = [pc1.createDataChannel('', options)];
+      bothOpen = Promise.all([
+        new Promise((r, e) => {
+          pair[0].onopen = r;
+          pair[0].onerror = ({error}) => e(error);
+        }),
+        new Promise((r, e) => pc2.ondatachannel = ({channel}) => {
+          pair[1] = channel;
+          channel.onopen = r;
+          channel.onerror = ({error}) => e(error);
+        })
+      ]);
+    }
+    exchangeIceCandidates(pc1, pc2);
+    await exchangeOfferAnswer(pc1, pc2);
+    await bothOpen;
+    return pair;
+  } finally {
+    for (const dc of pair) {
+       dc.onopen = dc.onerror = null;
+    }
+  }
+}
+
+// Wait for RTP and RTCP stats to arrive
+async function waitForRtpAndRtcpStats(pc) {
+  // If remote stats are never reported, return after 5 seconds.
+  const startTime = performance.now();
+  while (true) {
+    const report = await pc.getStats();
+    const stats = [...report.values()].filter(({type}) => type.endsWith("bound-rtp"));
+    // Each RTP and RTCP stat has a reference
+    // to the matching stat in the other direction
+    if (stats.length && stats.every(({localId, remoteId}) => localId || remoteId)) {
+      break;
+    }
+    if (performance.now() > startTime + 5000) {
+      break;
+    }
+  }
+}
+
+// Wait for a single message event and return
+// a promise that resolve when the event fires
+function awaitMessage(channel) {
+  const once = true;
+  return new Promise((resolve, reject) => {
+    channel.addEventListener('message', ({data}) => resolve(data), {once});
+    channel.addEventListener('error', reject, {once});
+  });
+}
+
+// Helper to convert a blob to array buffer so that
+// we can read the content
+async function blobToArrayBuffer(blob) {
+  const reader = new FileReader();
+  reader.readAsArrayBuffer(blob);
+  return new Promise((resolve, reject) => {
+    reader.addEventListener('load', () => resolve(reader.result), {once: true});
+    reader.addEventListener('error', () => reject(reader.error), {once: true});
+  });
+}
+
+// Assert that two TypedArray or ArrayBuffer objects have the same byte values
+function assert_equals_typed_array(array1, array2) {
+  const [view1, view2] = [array1, array2].map((array) => {
+    if (array instanceof ArrayBuffer) {
+      return new DataView(array);
+    } else {
+      assert_true(array.buffer instanceof ArrayBuffer,
+        'Expect buffer to be instance of ArrayBuffer');
+      return new DataView(array.buffer, array.byteOffset, array.byteLength);
+    }
+  });
+
+  assert_equals(view1.byteLength, view2.byteLength,
+    'Expect both arrays to be of the same byte length');
+
+  const byteLength = view1.byteLength;
+
+  for (let i = 0; i < byteLength; ++i) {
+    assert_equals(view1.getUint8(i), view2.getUint8(i),
+      `Expect byte at buffer position ${i} to be equal`);
+  }
+}
+
+// These media tracks will be continually updated with deterministic "noise" in
+// order to ensure UAs do not cease transmission in response to apparent
+// silence.
+//
+// > Many codecs and systems are capable of detecting "silence" and changing
+// > their behavior in this case by doing things such as not transmitting any
+// > media.
+//
+// Source: https://w3c.github.io/webrtc-pc/#offer-answer-options
+const trackFactories = {
+  // Share a single context between tests to avoid exceeding resource limits
+  // without requiring explicit destruction.
+  audioContext: null,
+
+  /**
+   * Given a set of requested media types, determine if the user agent is
+   * capable of procedurally generating a suitable media stream.
+   *
+   * @param {object} requested
+   * @param {boolean} [requested.audio] - flag indicating whether the desired
+   *                                      stream should include an audio track
+   * @param {boolean} [requested.video] - flag indicating whether the desired
+   *                                      stream should include a video track
+   *
+   * @returns {boolean}
+   */
+  canCreate(requested) {
+    const supported = {
+      audio: !!window.AudioContext && !!window.MediaStreamAudioDestinationNode,
+      video: !!HTMLCanvasElement.prototype.captureStream
+    };
+
+    return (!requested.audio || supported.audio) &&
+      (!requested.video || supported.video);
+  },
+
+  audio() {
+    const ctx = trackFactories.audioContext = trackFactories.audioContext ||
+      new AudioContext();
+    const oscillator = ctx.createOscillator();
+    const dst = oscillator.connect(ctx.createMediaStreamDestination());
+    oscillator.start();
+    return dst.stream.getAudioTracks()[0];
+  },
+
+  video({width = 640, height = 480, signal} = {}) {
+    const canvas = Object.assign(
+      document.createElement("canvas"), {width, height}
+    );
+    const ctx = canvas.getContext('2d');
+    const stream = canvas.captureStream();
+
+    let count = 0;
+    const interval = setInterval(() => {
+      ctx.fillStyle = `rgb(${count%255}, ${count*count%255}, ${count%255})`;
+      count += 1;
+      ctx.fillRect(0, 0, width, height);
+      // Add some bouncing boxes in contrast color to add a little more noise.
+      const contrast = count + 128;
+      ctx.fillStyle = `rgb(${contrast%255}, ${contrast*contrast%255}, ${contrast%255})`;
+      const xpos = count % (width - 20);
+      const ypos = count % (height - 20);
+      ctx.fillRect(xpos, ypos, xpos + 20, ypos + 20);
+      const xpos2 = (count + width / 2) % (width - 20);
+      const ypos2 = (count + height / 2) % (height - 20);
+      ctx.fillRect(xpos2, ypos2, xpos2 + 20, ypos2 + 20);
+      // If signal is set (0-255), add a constant-color box of that luminance to
+      // the video frame at coordinates 20 to 60 in both X and Y direction.
+      // (big enough to avoid color bleed from surrounding video in some codecs,
+      // for more stable tests).
+      if (signal != undefined) {
+        ctx.fillStyle = `rgb(${signal}, ${signal}, ${signal})`;
+        ctx.fillRect(20, 20, 40, 40);
+      }
+    }, 100);
+
+    if (document.body) {
+      document.body.appendChild(canvas);
+    } else {
+      document.addEventListener('DOMContentLoaded', () => {
+        document.body.appendChild(canvas);
+      }, {once: true});
+    }
+
+    // Implement track.stop() for performance in some tests on some platforms
+    const track = stream.getVideoTracks()[0];
+    const nativeStop = track.stop;
+    track.stop = function stop() {
+      clearInterval(interval);
+      nativeStop.apply(this);
+      if (document.body && canvas.parentElement == document.body) {
+        document.body.removeChild(canvas);
+      }
+    };
+    return track;
+  }
+};
+
+// Get the signal from a video element inserted by createNoiseStream
+function getVideoSignal(v) {
+  if (v.videoWidth < 60 || v.videoHeight < 60) {
+    throw new Error('getVideoSignal: video too small for test');
+  }
+  const canvas = document.createElement("canvas");
+  canvas.width = canvas.height = 60;
+  const context = canvas.getContext('2d');
+  context.drawImage(v, 0, 0);
+  // Extract pixel value at position 40, 40
+  const pixel = context.getImageData(40, 40, 1, 1);
+  // Use luma reconstruction to get back original value according to
+  // ITU-R rec BT.709
+  return (pixel.data[0] * 0.21 + pixel.data[1] * 0.72 + pixel.data[2] * 0.07);
+}
+
+async function detectSignal(t, v, value) {
+  while (true) {
+    const signal = getVideoSignal(v).toFixed();
+    // allow off-by-two pixel error (observed in some implementations)
+    if (value - 2 <= signal && signal <= value + 2) {
+      return;
+    }
+    // We would like to wait for each new frame instead here,
+    // but there seems to be no such callback.
+    await new Promise(r => t.step_timeout(r, 100));
+  }
+}
+
+// Generate a MediaStream bearing the specified tracks.
+//
+// @param {object} [caps]
+// @param {boolean} [caps.audio] - flag indicating whether the generated stream
+//                                 should include an audio track
+// @param {boolean} [caps.video] - flag indicating whether the generated stream
+//                                 should include a video track, or parameters for video
+async function getNoiseStream(caps = {}) {
+  if (!trackFactories.canCreate(caps)) {
+    return navigator.mediaDevices.getUserMedia(caps);
+  }
+  const tracks = [];
+
+  if (caps.audio) {
+    tracks.push(trackFactories.audio());
+  }
+
+  if (caps.video) {
+    tracks.push(trackFactories.video(caps.video));
+  }
+
+  return new MediaStream(tracks);
+}
+
+// Obtain a MediaStreamTrack of kind using procedurally-generated streams (and
+// falling back to `getUserMedia` when the user agent cannot generate the
+// requested streams).
+// Return Promise of pair of track and associated mediaStream.
+// Assumes that there is at least one available device
+// to generate the track.
+function getTrackFromUserMedia(kind) {
+  return getNoiseStream({ [kind]: true })
+  .then(mediaStream => {
+    const [track] = mediaStream.getTracks();
+    return [track, mediaStream];
+  });
+}
+
+// Obtain |count| MediaStreamTracks of type |kind| and MediaStreams. The tracks
+// do not belong to any stream and the streams are empty. Returns a Promise
+// resolved with a pair of arrays [tracks, streams].
+// Assumes there is at least one available device to generate the tracks and
+// streams and that the getUserMedia() calls resolve.
+function getUserMediaTracksAndStreams(count, type = 'audio') {
+  let otherTracksPromise;
+  if (count > 1)
+    otherTracksPromise = getUserMediaTracksAndStreams(count - 1, type);
+  else
+    otherTracksPromise = Promise.resolve([[], []]);
+  return otherTracksPromise.then(([tracks, streams]) => {
+    return getTrackFromUserMedia(type)
+    .then(([track, stream]) => {
+      // Remove the default stream-track relationship.
+      stream.removeTrack(track);
+      tracks.push(track);
+      streams.push(stream);
+      return [tracks, streams];
+    });
+  });
+}
+
+// Performs an offer exchange caller -> callee.
+async function exchangeOffer(caller, callee) {
+  await caller.setLocalDescription(await caller.createOffer());
+  await callee.setRemoteDescription(caller.localDescription);
+}
+// Performs an answer exchange caller -> callee.
+async function exchangeAnswer(caller, callee) {
+  // Note that caller's remote description must be set first; if not,
+  // there's a chance that candidates from callee arrive at caller before
+  // it has a remote description to apply them to.
+  const answer = await callee.createAnswer();
+  await caller.setRemoteDescription(answer);
+  await callee.setLocalDescription(answer);
+}
+async function exchangeOfferAnswer(caller, callee) {
+  await exchangeOffer(caller, callee);
+  await exchangeAnswer(caller, callee);
+}
+
+// The returned promise is resolved with caller's ontrack event.
+async function exchangeAnswerAndListenToOntrack(t, caller, callee) {
+  const ontrackPromise = addEventListenerPromise(t, caller, 'track');
+  await exchangeAnswer(caller, callee);
+  return ontrackPromise;
+}
+// The returned promise is resolved with callee's ontrack event.
+async function exchangeOfferAndListenToOntrack(t, caller, callee) {
+  const ontrackPromise = addEventListenerPromise(t, callee, 'track');
+  await exchangeOffer(caller, callee);
+  return ontrackPromise;
+}
+
+// The resolver extends a |promise| that can be resolved or rejected using |resolve|
+// or |reject|.
+class Resolver extends Promise {
+  constructor(executor) {
+    let resolve, reject;
+    super((resolve_, reject_) => {
+      resolve = resolve_;
+      reject = reject_;
+      if (executor) {
+        return executor(resolve_, reject_);
+      }
+    });
+
+    this._done = false;
+    this._resolve = resolve;
+    this._reject = reject;
+  }
+
+  /**
+   * Return whether the promise is done (resolved or rejected).
+   */
+  get done() {
+    return this._done;
+  }
+
+  /**
+   * Resolve the promise.
+   */
+  resolve(...args) {
+    this._done = true;
+    return this._resolve(...args);
+  }
+
+  /**
+   * Reject the promise.
+   */
+  reject(...args) {
+    this._done = true;
+    return this._reject(...args);
+  }
+}
+
+function addEventListenerPromise(t, obj, type, listener) {
+  if (!listener) {
+    return waitUntilEvent(obj, type);
+  }
+  return new Promise(r => obj.addEventListener(type,
+                                               t.step_func(e => r(listener(e))),
+                                               {once: true}));
+}
+
+function createPeerConnectionWithCleanup(t) {
+  const pc = new RTCPeerConnection();
+  t.add_cleanup(() => pc.close());
+  return pc;
+}
+
+async function createTrackAndStreamWithCleanup(t, kind = 'audio') {
+  let constraints = {};
+  constraints[kind] = true;
+  const stream = await getNoiseStream(constraints);
+  const [track] = stream.getTracks();
+  t.add_cleanup(() => track.stop());
+  return [track, stream];
+}
+
+function findTransceiverForSender(pc, sender) {
+  const transceivers = pc.getTransceivers();
+  for (let i = 0; i < transceivers.length; ++i) {
+    if (transceivers[i].sender == sender)
+      return transceivers[i];
+  }
+  return null;
+}
+
+function preferCodec(transceiver, mimeType, sdpFmtpLine) {
+  const {codecs} = RTCRtpSender.getCapabilities(transceiver.receiver.track.kind);
+  // sdpFmtpLine is optional, pick the first partial match if not given.
+  const selectedCodecIndex = codecs.findIndex(c => {
+    return c.mimeType === mimeType && (c.sdpFmtpLine === sdpFmtpLine || !sdpFmtpLine);
+  });
+  const selectedCodec = codecs[selectedCodecIndex];
+  codecs.slice(selectedCodecIndex, 1);
+  codecs.unshift(selectedCodec);
+  return transceiver.setCodecPreferences(codecs);
+}
+
+// Contains a set of values and will yell at you if you try to add a value twice.
+class UniqueSet extends Set {
+  constructor(items) {
+    super();
+    if (items !== undefined) {
+      for (const item of items) {
+        this.add(item);
+      }
+    }
+  }
+
+  add(value, message) {
+    if (message === undefined) {
+      message = `Value '${value}' needs to be unique but it is already in the set`;
+    }
+    assert_true(!this.has(value), message);
+    super.add(value);
+  }
+}
+
+const iceGatheringStateTransitions = async (pc, ...states) => {
+  for (const state of states) {
+    await new Promise((resolve, reject) => {
+      pc.addEventListener('icegatheringstatechange', () => {
+        if (pc.iceGatheringState == state) {
+          resolve();
+        } else {
+          reject(`Unexpected gathering state: ${pc.iceGatheringState}, was expecting ${state}`);
+        }
+      }, {once: true});
+    });
+  }
+};
+
+const initialOfferAnswerWithIceGatheringStateTransitions =
+    async (pc1, pc2, offerOptions) => {
+      await pc1.setLocalDescription(
+        await pc1.createOffer(offerOptions));
+      const pc1Transitions =
+          iceGatheringStateTransitions(pc1, 'gathering', 'complete');
+      await pc2.setRemoteDescription(pc1.localDescription);
+      await pc2.setLocalDescription(await pc2.createAnswer());
+      const pc2Transitions =
+          iceGatheringStateTransitions(pc2, 'gathering', 'complete');
+      await pc1.setRemoteDescription(pc2.localDescription);
+      await pc1Transitions;
+      await pc2Transitions;
+    };
+
+const expectNoMoreGatheringStateChanges = async (t, pc) => {
+  pc.onicegatheringstatechange =
+      t.step_func(() => {
+        assert_unreached(
+            'Should not get an icegatheringstatechange right now!');
+      });
+};