Add number of quality adapt changes to VideoSendStream stats.

webrtc/video/send_statistics_proxy.cc

Index: webrtc/video/send_statistics_proxy.cc
diff --git a/webrtc/video/send_statistics_proxy.cc b/webrtc/video/send_statistics_proxy.cc
index 7cefa294e60cdf4741f685220ee0136762d3081f..464e1a18bf762bd5aab082092753912cb4315d40 100644
--- a/webrtc/video/send_statistics_proxy.cc
+++ b/webrtc/video/send_statistics_proxy.cc
@@ -699,6 +699,7 @@ void SendStatisticsProxy::OnCpuRestrictedResolutionChanged(
 void SendStatisticsProxy::OnQualityRestrictedResolutionChanged(
     int num_quality_downscales) {
   rtc::CritScope lock(&crit_);
+  ++stats_.number_of_quality_adapt_changes;
   quality_downscales_ = num_quality_downscales;
   stats_.bw_limited_resolution = quality_downscales_ > 0;
 }