Whitelist qualityLimitationResolutionChanges

The stat has recently been added to the RTCOutboundRtpStreamStats
https://w3c.github.io/webrtc-stats/#dom-rtcoutboundrtpstreamstats-qualitylimitationresolutionchanges

Bug: webrtc:10935
Change-Id: I97ba38b373996f4994a905ca7e9a5bb12ce13b57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1777681
Commit-Queue: Evan Shrubsole <eshr@google.com>
Reviewed-by: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693177}

chrome/test/data/webrtc/peerconnection_getstats.js

@@ -190,6 +190,7 @@ let kRTCOutboundRtpStreamStats = new RTCStats(kRTCSentRtpStreamStats, {
   averageRtcpInterval: 'number',
   qualityLimitationReason: 'string',
   qualityLimitationDurations: 'object',
+  qualityLimitationResolutionChanges: 'number',
   perDscpPacketsSent: 'object',
   nackCount: 'number',
   firCount: 'number',