Add new event type to RtcEventLog

Alr state is now logged by the pacer. To avoid confusion,
loopback tools will now create two separate rtc event
logs for sender and receiver calls.

Bug: webrtc:8287, webrtc:8588
Change-Id: Ib3e47d109c3a65a7ed069b9a613e6a08fe6a2f30
Reviewed-on: https://webrtc-review.googlesource.com/26880
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21084}
diff --git a/logging/rtc_event_log/encoder/rtc_event_log_encoder_legacy.h b/logging/rtc_event_log/encoder/rtc_event_log_encoder_legacy.h
index b0909e2..f4d3355 100644
--- a/logging/rtc_event_log/encoder/rtc_event_log_encoder_legacy.h
+++ b/logging/rtc_event_log/encoder/rtc_event_log_encoder_legacy.h
@@ -42,6 +42,7 @@
 class RtcEventRtpPacketOutgoing;
 class RtcEventVideoReceiveStreamConfig;
 class RtcEventVideoSendStreamConfig;
+class RtcEventAlrState;
 class RtpPacket;
 
 class RtcEventLogEncoderLegacy final : public RtcEventLogEncoder {
@@ -52,6 +53,7 @@
 
  private:
   // Encoding entry-point for the various RtcEvent subclasses.
+  std::string EncodeAlrState(const RtcEventAlrState& event);
   std::string EncodeAudioNetworkAdaptation(
       const RtcEventAudioNetworkAdaptation& event);
   std::string EncodeAudioPlayout(const RtcEventAudioPlayout& event);