Add the internals of RtcEvent's subclasses

webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.cc

Index: webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.cc
diff --git a/webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.cc b/webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.cc
index 6cc76c8e29db4ea7578ca1fc7c448b43b43724c6..f5dacf061cac34818f34bb620bb9a682fa04a2cc 100644
--- a/webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.cc
+++ b/webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.cc
@@ -12,6 +12,8 @@
 
 namespace webrtc {
 
+RtcEventAudioPlayout::RtcEventAudioPlayout(uint32_t ssrc) : ssrc_(ssrc) {}
+
 RtcEvent::Type RtcEventAudioPlayout::GetType() const {
   return RtcEvent::Type::AudioPlayout;
 }