Fix RTCPeerConnection-track-stats.https.html expectations.

The tests started failing in an earlier WPT import, see
https://crbug.com/832501.

TBR=hta@chromium.org

Bug: 832501
Change-Id: If53c927e03dabb60158c61befc5a29d1c45bba1f
Reviewed-on: https://chromium-review.googlesource.com/c/1394307Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619631}

third_party/blink/web_tests/TestExpectations

@@ -3208,10 +3208,6 @@ crbug.com/893490 [ Mac ] external/wpt/css/css-text/white-space/control-chars-09F
 crbug.com/893480 external/wpt/infrastructure/testdriver/actions/elementTiming.html [ Timeout ]
 crbug.com/893480 external/wpt/infrastructure/testdriver/actions/multiDevice.html [ Failure Timeout ]
 
-# wpt-importer has trouble rebaselining these tests. They might be flaky?
-crbug.com/832501 external/wpt/webrtc/RTCPeerConnection-track-stats.https.html [ Failure ]
-crbug.com/832501 virtual/webrtc-wpt-unified-plan/external/wpt/webrtc/RTCPeerConnection-track-stats.https.html [ Failure ]
-
 # Hit a DCHECK
 crbug.com/918664 external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/sizing/block-size-with-min-or-max-content-table-1a.html [ Failure Pass ]
 

third_party/blink/web_tests/external/wpt/webrtc/RTCPeerConnection-track-stats.https-expected.txt

+This is a testharness.js-based test.
+PASS addTrack() without setLocalDescription() yields track stats
+PASS addTrack() without setLocalDescription() yields media stream stats
+PASS addTrack() with setLocalDescription() yields track stats
+PASS addTrack() with setLocalDescription() yields media stream stats
+PASS addTrack(): Media stream stats references track stats
+PASS Media stream stats references track stats
+PASS O/A exchange yields outbound RTP stream stats for sending track
+PASS O/A exchange yields inbound RTP stream stats for receiving track
+PASS replaceTrack() before offer: new track attachment stats present
+PASS replaceTrack() after offer, before answer: new track attachment stats present
+PASS replaceTrack() after answer: new track attachment stats present
+FAIL replaceTrack(): original track attachment stats present after replacing assert_true: Has stats for original track expected true got false
+PASS RTCRtpSender.getStats() contains only outbound-rtp and related stats
+PASS RTCRtpReceiver.getStats() contains only inbound-rtp and related stats
+PASS RTCPeerConnection.getStats(sendingTrack) is the same as RTCRtpSender.getStats()
+PASS RTCPeerConnection.getStats(receivingTrack) is the same as RTCRtpReceiver.getStats()
+PASS RTCPeerConnection.getStats(track) throws InvalidAccessError when there are zero senders or receivers for the track
+PASS RTCPeerConnection.getStats(track) throws InvalidAccessError when there are multiple senders for the track
+Harness: the test ran to completion.
+