Add accessor for UTC start time in event log

Bug: webrtc:11933
Change-Id: Id9e63dc0487d5d07ac87e319695206ee4cd627e8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/219787
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34079}
diff --git a/logging/rtc_event_log/logged_events.h b/logging/rtc_event_log/logged_events.h
index da7653d..3824494 100644
--- a/logging/rtc_event_log/logged_events.h
+++ b/logging/rtc_event_log/logged_events.h
@@ -249,6 +249,8 @@
   int64_t log_time_us() const { return timestamp_us; }
   int64_t log_time_ms() const { return timestamp_us / 1000; }
 
+  Timestamp utc_time() const { return Timestamp::Millis(utc_start_time_ms); }
+
   int64_t timestamp_us;
   int64_t utc_start_time_ms;
 };