Use default header extension map in rtc_event_log2text

Use defaults if the header extension map is missing from the config.

BUG=webrtc:6399

Review-Url: https://codereview.webrtc.org/2983283002
Cr-Commit-Position: refs/heads/master@{#19267}
diff --git a/webrtc/rtc_tools/event_log_visualizer/analyzer.cc b/webrtc/rtc_tools/event_log_visualizer/analyzer.cc
index b42f082..593a3b8 100644
--- a/webrtc/rtc_tools/event_log_visualizer/analyzer.cc
+++ b/webrtc/rtc_tools/event_log_visualizer/analyzer.cc
@@ -119,8 +119,20 @@
 webrtc::RtpHeaderExtensionMap GetDefaultHeaderExtensionMap() {
   webrtc::RtpHeaderExtensionMap default_map;
   default_map.Register<AudioLevel>(webrtc::RtpExtension::kAudioLevelDefaultId);
+  default_map.Register<TransmissionOffset>(
+      webrtc::RtpExtension::kTimestampOffsetDefaultId);
   default_map.Register<AbsoluteSendTime>(
       webrtc::RtpExtension::kAbsSendTimeDefaultId);
+  default_map.Register<VideoOrientation>(
+      webrtc::RtpExtension::kVideoRotationDefaultId);
+  default_map.Register<VideoContentTypeExtension>(
+      webrtc::RtpExtension::kVideoContentTypeDefaultId);
+  default_map.Register<VideoTimingExtension>(
+      webrtc::RtpExtension::kVideoTimingDefaultId);
+  default_map.Register<TransportSequenceNumber>(
+      webrtc::RtpExtension::kTransportSequenceNumberDefaultId);
+  default_map.Register<PlayoutDelayLimits>(
+      webrtc::RtpExtension::kPlayoutDelayDefaultId);
   return default_map;
 }