diff --git a/webrtc/RTCDataChannel-send.html b/webrtc/RTCDataChannel-send.html
index 7cacaa4d37bb76..cb8b4edc3fae15 100644
--- a/webrtc/RTCDataChannel-send.html
+++ b/webrtc/RTCDataChannel-send.html
@@ -14,7 +14,7 @@
   //  createDataChannelPair
   //  awaitMessage
   //  blobToArrayBuffer
-  //  assert_equals_array_buffer
+  //  assert_equals_typed_array
 
   /*
     6.2.  RTCDataChannel
@@ -140,7 +140,7 @@
       assert_true(messageBuffer instanceof ArrayBuffer,
         'Expect messageBuffer to be an ArrayBuffer');
 
-      assert_equals_array_buffer(messageBuffer, helloBuffer.buffer);
+      assert_equals_typed_array(messageBuffer, helloBuffer.buffer);
     });
   }, 'Data channel should be able to send Uint8Array message and receive as ArrayBuffer');
 
@@ -162,7 +162,7 @@
       assert_true(messageBuffer instanceof ArrayBuffer,
         'Expect messageBuffer to be an ArrayBuffer');
 
-      assert_equals_array_buffer(messageBuffer, helloBuffer.buffer);
+      assert_equals_typed_array(messageBuffer, helloBuffer.buffer);
     });
   }, 'Data channel should be able to send ArrayBuffer message and receive as ArrayBuffer');
 
@@ -183,7 +183,7 @@
       assert_true(messageBuffer instanceof ArrayBuffer,
         'Expect messageBuffer to be an ArrayBuffer');
 
-      assert_equals_array_buffer(messageBuffer, helloBuffer.buffer);
+      assert_equals_typed_array(messageBuffer, helloBuffer.buffer);
     });
   }, 'Data channel should be able to send Blob message and receive as ArrayBuffer');
 
@@ -210,7 +210,7 @@
       assert_true(messageBuffer instanceof ArrayBuffer,
         'Expect messageBuffer to be an ArrayBuffer');
 
-      assert_equals_array_buffer(messageBuffer, helloBuffer.buffer);
+      assert_equals_typed_array(messageBuffer, helloBuffer.buffer);
     });
   }, 'Data channel should be able to send ArrayBuffer message and receive as Blob');
 
@@ -240,7 +240,7 @@
       assert_true(messageBuffer instanceof ArrayBuffer,
         'Expect messageBuffer to be an ArrayBuffer');
 
-      assert_equals_array_buffer(messageBuffer, helloBuffer.buffer);
+      assert_equals_typed_array(messageBuffer, helloBuffer.buffer);
     });
   }, 'Data channel binaryType should receive message as Blob by default');
 
@@ -253,9 +253,9 @@
       receivedMessages.push(data);
 
       if(receivedMessages.length === 3) {
-        assert_equals_array_buffer(receivedMessages[0], helloBuffer.buffer);
+        assert_equals_typed_array(receivedMessages[0], helloBuffer.buffer);
         assert_equals(receivedMessages[1], unicodeString);
-        assert_equals_array_buffer(receivedMessages[2], helloBuffer.buffer);
+        assert_equals_typed_array(receivedMessages[2], helloBuffer.buffer);
 
         t.done();
       }
diff --git a/webrtc/RTCPeerConnection-helper.js b/webrtc/RTCPeerConnection-helper.js
index 9baf840df21321..a2a3e296462bfc 100644
--- a/webrtc/RTCPeerConnection-helper.js
+++ b/webrtc/RTCPeerConnection-helper.js
@@ -159,39 +159,95 @@ function test_never_resolve(testFunc, testName) {
   }, testName);
 }
 
+// Helper class to queue ICE candidates of a peer connection
+// Can be passed to `exchangeIceCandidates` which will automatically empty the queue.
+class IceCandidateQueue {
+  constructor(pc) {
+    this.pc = pc;
+    this._queue = [];
+    this._listener = (event) => this._handleIceCandidate(event);
+
+    // Queue ICE candidates
+    this.pc.addEventListener('icecandidate', this._listener);
+  }
+
+  // Unbind the event listener and return all queued candidates
+  disband() {
+    this.pc.removeEventListener('icecandidate', this._listener);
+    return this._queue;
+  }
+
+  _handleIceCandidate(event) {
+    this._queue.push(event.candidate);
+  }
+}
+
 // 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;
+function exchangeIceCandidates(pc1OrQueue, pc2OrQueue) {
+  const handleCandidate = (remotePc, candidate) => {
+    // candidate may be null to indicate end of candidate gathering.
+    // There is ongoing discussion on w3c/webrtc-pc#1213
+    // that there should be an empty candidate string event
+    // for end of candidate for each m= section.
+    if (candidate && remotePc.signalingState !== 'closed') {
+      remotePc.addIceCandidate(candidate);
+    }
+  };
+
+  const exchangeCandidates = (localPcOrQueue, remotePcOrQueue) => {
+    let localPc = localPcOrQueue;
+    let remotePc = remotePcOrQueue;
+    if (remotePcOrQueue instanceof IceCandidateQueue) {
+      remotePc = remotePcOrQueue.pc;
+    }
 
-      // candidate may be null to indicate end of candidate gathering.
-      // There is ongoing discussion on w3c/webrtc-pc#1213
-      // that there should be an empty candidate string event
-      // for end of candidate for each m= section.
-      if(candidate && remotePc.signalingState !== 'closed') {
-        remotePc.addIceCandidate(candidate);
+    // Queue? Disband it first
+    if (localPcOrQueue instanceof IceCandidateQueue) {
+      localPc = localPcOrQueue.pc;
+      for (const candidate of localPcOrQueue.disband()) {
+        handleCandidate(remotePc, candidate);
       }
+    }
+
+    // Exchange further candidates
+    localPc.addEventListener('icecandidate', event => {
+      const { candidate } = event;
+      handleCandidate(remotePc, candidate);
     });
-  }
+  };
 
-  doExchange(pc1, pc2);
-  doExchange(pc2, pc1);
+  exchangeCandidates(pc1OrQueue, pc2OrQueue);
+  exchangeCandidates(pc2OrQueue, pc1OrQueue);
 }
 
 // Helper function for doing one round of offer/answer exchange
 // betweeen two local peer connections
-function doSignalingHandshake(localPc, remotePc) {
+function doSignalingHandshake(localPc, remotePc, options={}) {
   return localPc.createOffer()
-  .then(offer => Promise.all([
-    localPc.setLocalDescription(offer),
-    remotePc.setRemoteDescription(offer)]))
+  .then(offer => {
+    // Modify offer if callback has been provided
+    if (options.modifyOffer) {
+      offer = options.modifyOffer(offer);
+    }
+
+    // Apply offer
+    return Promise.all([
+      localPc.setLocalDescription(offer),
+      remotePc.setRemoteDescription(offer)])
+  })
   .then(() => remotePc.createAnswer())
-  .then(answer => Promise.all([
-    remotePc.setLocalDescription(answer),
-    localPc.setRemoteDescription(answer)]))
+  .then(answer => {
+    // Modify answer if callback has been provided
+    if (options.modifyAnswer) {
+      answer = options.modifyAnswer(answer);
+    }
+
+    // Apply answer
+    return Promise.all([
+      remotePc.setLocalDescription(answer),
+      localPc.setRemoteDescription(answer)])
+  });
 }
 
 // Helper function to create a pair of connected data channel.
@@ -295,23 +351,25 @@ function blobToArrayBuffer(blob) {
   });
 }
 
-// Assert that two ArrayBuffer objects have the same byte values
-function assert_equals_array_buffer(buffer1, buffer2) {
-  assert_true(buffer1 instanceof ArrayBuffer,
-    'Expect buffer to be instance of ArrayBuffer');
-
-  assert_true(buffer2 instanceof ArrayBuffer,
-    'Expect buffer to be instance of ArrayBuffer');
+// 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(buffer1.byteLength, buffer2.byteLength,
-    'Expect both array buffers to be of the same byte length');
+  assert_equals(view1.byteLength, view2.byteLength,
+    'Expect both arrays to be of the same byte length');
 
-  const byteLength = buffer1.byteLength;
-  const byteArray1 = new Uint8Array(buffer1);
-  const byteArray2 = new Uint8Array(buffer2);
+  const byteLength = view1.byteLength;
 
-  for(let i=0; i<byteLength; i++) {
-    assert_equals(byteArray1[i], byteArray2[i],
+  for (let i = 0; i < byteLength; ++i) {
+    assert_equals(view1.getUint8(i), view2.getUint8(i),
       `Expect byte at buffer position ${i} to be equal`);
   }
 }
@@ -478,18 +536,45 @@ async function exchangeOfferAndListenToOntrack(t, caller, callee) {
   return ontrackPromise;
 }
 
-// The resolver has a |promise| that can be resolved or rejected using |resolve|
+// The resolver extends a |promise| that can be resolved or rejected using |resolve|
 // or |reject|.
-class Resolver {
-  constructor() {
-    let promiseResolve;
-    let promiseReject;
-    this.promise = new Promise(function(resolve, reject) {
-      promiseResolve = resolve;
-      promiseReject = reject;
+class Resolver extends Promise {
+  constructor(executor) {
+    let resolve, reject;
+    super((resolve_, reject_) => {
+      resolve = resolve_;
+      reject = reject_;
+      if (executor) {
+        return executor(resolve_, reject_);
+      }
     });
-    this.resolve = promiseResolve;
-    this.reject = promiseReject;
+
+    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);
   }
 }
 
@@ -526,3 +611,23 @@ function findTransceiverForSender(pc, sender) {
   }
   return null;
 }
+
+// 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);
+  }
+}
diff --git a/webrtc/tools/.eslintrc.js b/webrtc/tools/.eslintrc.js
index 1778f8505e04cf..914a09dc32c741 100644
--- a/webrtc/tools/.eslintrc.js
+++ b/webrtc/tools/.eslintrc.js
@@ -105,7 +105,7 @@ module.exports = {
     createDataChannelPair: true,
     awaitMessage: true,
     blobToArrayBuffer: true,
-    assert_equals_array_buffer: true,
+    assert_equals_typed_array: true,
     generateMediaStreamTrack: true,
     getTrackFromUserMedia: true,
     getUserMediaTracksAndStreams: true,