Add the internals of RtcEvent's subclasses

webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.h

Index: webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.h
diff --git a/webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.h b/webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.h
index df430b83eb2e9b46bf9ffa1697a963cda45f51d9..90199efd8512074e8eb79bf4a2eeff3de5f23fe2 100644
--- a/webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.h
+++ b/webrtc/logging/rtc_event_log/events/rtc_event_audio_playout.h
@@ -17,11 +17,14 @@ namespace webrtc {
 
 class RtcEventAudioPlayout final : public RtcEvent {
  public:
+  explicit RtcEventAudioPlayout(uint32_t ssrc);
   ~RtcEventAudioPlayout() override = default;
 
   Type GetType() const override;
 
   bool IsConfigEvent() const override;
+
+  const uint32_t ssrc_;
 };
 
 }  // namespace webrtc