Cast: Add missing enum and PacketEvent field to cast_messages.

media/cast/logging/logging_defines.h

Index: media/cast/logging/logging_defines.h
diff --git a/media/cast/logging/logging_defines.h b/media/cast/logging/logging_defines.h
index 2af95d62d3f51174c8c823a1d9a7e260609beeb2..b3f3841ffb31aae87f6349c12214feb239f955c6 100644
--- a/media/cast/logging/logging_defines.h
+++ b/media/cast/logging/logging_defines.h
@@ -40,7 +40,12 @@ enum CastLoggingEvent {
 const char* CastLoggingToString(CastLoggingEvent event);
 
 // CastLoggingEvent are classified into one of three following types.
-enum EventMediaType { AUDIO_EVENT, VIDEO_EVENT, UNKNOWN_EVENT };
+enum EventMediaType {
+  AUDIO_EVENT,
+  VIDEO_EVENT,
+  UNKNOWN_EVENT,
+  EVENT_MEDIA_TYPE_LAST = UNKNOWN_EVENT
+};
 
 struct FrameEvent {
   FrameEvent();