Hooked up RtcEventLog. It lives in Voice Engine and pointers are propagated to ACM and Call.

webrtc/modules/audio_coding/main/acm2/audio_coding_module_impl.cc

Index: webrtc/modules/audio_coding/main/acm2/audio_coding_module_impl.cc
diff --git a/webrtc/modules/audio_coding/main/acm2/audio_coding_module_impl.cc b/webrtc/modules/audio_coding/main/acm2/audio_coding_module_impl.cc
index 9c3183271b75bcbdaca46d20cd915d8ecee05323..6b5552e95dd5dead7f1c7b8a85c1482d59277cff 100644
--- a/webrtc/modules/audio_coding/main/acm2/audio_coding_module_impl.cc
+++ b/webrtc/modules/audio_coding/main/acm2/audio_coding_module_impl.cc
@@ -27,6 +27,7 @@
 #include "webrtc/system_wrappers/interface/rw_lock_wrapper.h"
 #include "webrtc/system_wrappers/interface/trace.h"
 #include "webrtc/typedefs.h"
+#include "webrtc/video/rtc_event_log.h"
 
 namespace webrtc {
 
@@ -145,7 +146,9 @@ AudioCodingModuleImpl::AudioCodingModuleImpl(
       first_frame_(true),
       callback_crit_sect_(CriticalSectionWrapper::CreateCriticalSection()),
       packetization_callback_(NULL),
-      vad_callback_(NULL) {
+      vad_callback_(NULL),
+      event_log_crit_sect_(CriticalSectionWrapper::CreateCriticalSection()),
+      event_log_(nullptr) {
   if (InitializeReceiverSafe() < 0) {
     WEBRTC_TRACE(webrtc::kTraceError, webrtc::kTraceAudioCoding, id_,
                  "Cannot initialize receiver");
@@ -736,6 +739,11 @@ int AudioCodingModuleImpl::PlayoutData10Ms(int desired_freq_hz,
                  "PlayoutData failed, RecOut Failed");
     return -1;
   }
+  {
+    CriticalSectionScoped lock(event_log_crit_sect_);
+    if (event_log_)
+      event_log_->LogDebugEvent(RtcEventLog::DebugEvent::kAudioPlayout);
+  }
 
   audio_frame->id_ = id_;
   return 0;
@@ -971,6 +979,11 @@ void AudioCodingModuleImpl::DisableNack() {
   receiver_.DisableNack();
 }
 
+void AudioCodingModuleImpl::SetEventLog(RtcEventLog* event_log) {
+  CriticalSectionScoped lock(event_log_crit_sect_);
+  event_log_ = event_log;
+}
+
 std::vector<uint16_t> AudioCodingModuleImpl::GetNackList(
     int64_t round_trip_time_ms) const {
   return receiver_.GetNackList(round_trip_time_ms);