stats: convert qualitylimitationdurations to seconds

the internal value is defined milliseconds
  https://webrtc.googlesource.com/src/+/refs/heads/main/video/g3doc/stats.md
while the specification defines it in seconds
  https://w3c.github.io/webrtc-stats/#dom-rtcoutboundrtpstreamstats-qualitylimitationdurations

BUG=webrtc:13548,webrtc:10686

Change-Id: I901c84214c77dd5a6e59f6556a029c8e20cb7672
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/245482
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/main@{#35657}
diff --git a/pc/rtc_stats_collector.cc b/pc/rtc_stats_collector.cc
index 4735805..8b6a5fb 100644
--- a/pc/rtc_stats_collector.cc
+++ b/pc/rtc_stats_collector.cc
@@ -269,9 +269,12 @@
 QualityLimitationDurationToRTCQualityLimitationDuration(
     std::map<webrtc::QualityLimitationReason, int64_t> durations_ms) {
   std::map<std::string, double> result;
+  // The internal duration is defined in milliseconds while the spec defines
+  // the value in seconds:
+  // https://w3c.github.io/webrtc-stats/#dom-rtcoutboundrtpstreamstats-qualitylimitationdurations
   for (const auto& elem : durations_ms) {
     result[QualityLimitationReasonToRTCQualityLimitationReason(elem.first)] =
-        elem.second;
+        elem.second / static_cast<double>(rtc::kNumMillisecsPerSec);
   }
   return result;
 }