Experiment for the nack module.

webrtc/modules/video_coding/nack_module.cc

Index: webrtc/modules/video_coding/nack_module.cc
diff --git a/webrtc/modules/video_coding/nack_module.cc b/webrtc/modules/video_coding/nack_module.cc
index 319a902ca28f3c289cf3cb743687a0aab48670b8..80f84968eb1c50c13567a1ebabce3b118d4b9644 100644
--- a/webrtc/modules/video_coding/nack_module.cc
+++ b/webrtc/modules/video_coding/nack_module.cc
@@ -118,6 +118,12 @@ void NackModule::UpdateRtt(int64_t rtt_ms) {
   rtt_ms_ = rtt_ms;
 }
 
+void NackModule::Clear() {
+  rtc::CritScope lock(&crit_);
+  nack_list_.clear();
+  keyframe_list_.clear();
+}
+
 void NackModule::Stop() {
   rtc::CritScope lock(&crit_);
   running_ = false;