Add the internals of RtcEvent's subclasses

webrtc/logging/rtc_event_log/events/rtc_event_logging_started.cc

Index: webrtc/logging/rtc_event_log/events/rtc_event_logging_started.cc
diff --git a/webrtc/logging/rtc_event_log/events/rtc_event_logging_started.cc b/webrtc/logging/rtc_event_log/events/rtc_event_logging_started.cc
index 94022caf396e108ae5e956f82fc592e01b53cbec..4066d01c6d9b2ef1b99e376c0e3d30e1e4678a63 100644
--- a/webrtc/logging/rtc_event_log/events/rtc_event_logging_started.cc
+++ b/webrtc/logging/rtc_event_log/events/rtc_event_logging_started.cc
@@ -12,6 +12,9 @@
 
 namespace webrtc {
 
+RtcEventLoggingStarted::RtcEventLoggingStarted(int64_t timestamp_us)
+    : timestamp_us_(timestamp_us) {}
+
 RtcEvent::Type RtcEventLoggingStarted::GetType() const {
   return RtcEvent::Type::LoggingStarted;
 }