Add test for candidates always arriving after SLD resolves

Bug: chromium:1127309
Change-Id: I90602856ef9b021bf617fa8a7c95d872f87a8148
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2423886Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810157}

third_party/blink/web_tests/external/wpt/webrtc/protocol/candidate-exchange.https.html

@@ -186,6 +186,33 @@ promise_test(async t => {
   assert_array_equals(pc2IceStates.events, ['new', 'checking', 'connected']);
 }, 'Explicit offer/answer exchange gives a connection');
 
+promise_test(async t => {
+  const pc1 = new RTCPeerConnection();
+  t.add_cleanup(() => pc1.close());
+  pc1.createDataChannel('datachannel');
+  pc1.onicecandidate = assert_unreached;
+  const offer = await pc1.createOffer();
+  await pc1.setLocalDescription(offer);
+  await new Promise(resolve => {
+    pc1.onicecandidate = resolve;
+  });
+}, 'Candidates always arrive after setLocalDescription(offer) resolves');
+
+promise_test(async t => {
+  const pc1 = new RTCPeerConnection();
+  const pc2 = new RTCPeerConnection();
+  t.add_cleanup(() => pc1.close());
+  t.add_cleanup(() => pc2.close());
+  pc1.createDataChannel('datachannel');
+  pc2.onicecandidate = assert_unreached;
+  const offer = await pc1.createOffer();
+  await pc2.setRemoteDescription(offer);
+  await pc2.setLocalDescription(await pc2.createAnswer());
+  await new Promise(resolve => {
+    pc2.onicecandidate = resolve;
+  });
+}, 'Candidates always arrive after setLocalDescription(answer) resolves');
+
 </script>
 </body>
 </html>

third_party/blink/web_tests/virtual/webrtc-wpt-plan-b/external/wpt/webrtc/protocol/candidate-exchange.https-expected.txt

@@ -4,5 +4,7 @@ FAIL Adding only caller -> callee candidates gives a connection promise_test: Un
 FAIL Adding only callee -> caller candidates gives a connection promise_test: Unhandled rejection with value: object "TypeError: Cannot read property 'transport' of null"
 FAIL Adding callee -> caller candidates from end-of-candidates gives a connection promise_test: Unhandled rejection with value: object "TypeError: Cannot read property 'transport' of null"
 FAIL Explicit offer/answer exchange gives a connection promise_test: Unhandled rejection with value: object "TypeError: Cannot read property 'transport' of null"
+PASS Candidates always arrive after setLocalDescription(offer) resolves
+PASS Candidates always arrive after setLocalDescription(answer) resolves
 Harness: the test ran to completion.