Enable adaptive threshold experiment by default.

webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc

Index: webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
diff --git a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
index 4820e6295f7296a089fb53637ab795b4fbe33f57..c6d0c8828052be1d9803893afebde13000cd5c2f 100644
--- a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
+++ b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
@@ -44,7 +44,7 @@ AimdRateControl::AimdRateControl()
       beta_(0.85f),
       rtt_(kDefaultRttMs),
       time_of_last_log_(-1),
-      in_experiment_(AdaptiveThresholdExperimentIsEnabled()) {}
+      in_experiment_(!AdaptiveThresholdExperimentIsDisabled()) {}
 
 void AimdRateControl::SetMinBitrate(int min_bitrate_bps) {
   min_configured_bitrate_bps_ = min_bitrate_bps;