wpt: dont fire RTCPeerConnection.onconnectionstatechange on close

adds a test to assert that RTCPeerConnection.onconnectionstatechange
is not fired when RTCPeerConnection.close() is called.

BUG=699036,1023736

Change-Id: I623deeb4f0948cf213ff8913c33610ef0e7315e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1959969Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/master@{#727996}

third_party/blink/web_tests/external/wpt/webrtc/RTCPeerConnection-connectionState.https.html

@@ -270,4 +270,22 @@
 
     assert_array_equals(states, ['connecting', 'connected']);
   }, 'connectionState transitions to connected via connecting');
+
+  promise_test(async t => {
+    const pc1 = new RTCPeerConnection();
+    t.add_cleanup(() => pc1.close());
+    const pc2 = new RTCPeerConnection();
+    const stream = await getNoiseStream({ audio: true });
+    t.add_cleanup(() => stream.getTracks().forEach(track => track.stop()));
+
+    stream.getTracks().forEach(track => pc1.addTrack(track, stream));
+    exchangeIceCandidates(pc1, pc2);
+    doSignalingHandshake(pc1, pc2);
+    await listenToIceConnected(pc2);
+
+    pc2.onconnectionstatechange = t.unreached_func();
+    pc2.close();
+    assert_true(pc2.connectionState === 'closed');
+    await new Promise(r => t.step_timeout(r, 100));
+  }, 'Closing a PeerConnection should not fire connectionstatechange event');
 </script>

third_party/blink/web_tests/virtual/webrtc-wpt-plan-b/external/wpt/webrtc/RTCPeerConnection-connectionState.https-expected.txt

@@ -5,5 +5,6 @@ PASS connection with one data channel should eventually have connected connectio
 FAIL connection with one data channel should eventually have transports in connected state Cannot read property 'transport' of null
 PASS connectionState remains new when not adding remote ice candidates
 PASS connectionState transitions to connected via connecting
+PASS Closing a PeerConnection should not fire connectionstatechange event
 Harness: the test ran to completion.