Remove the VoiceEngineObserver callback interface.

BUG=webrtc:4690
TBR=kwiberg@webrtc.org

Review-Url: https://codereview.webrtc.org/3019513002
Cr-Commit-Position: refs/heads/master@{#19976}
diff --git a/voice_engine/shared_data.cc b/voice_engine/shared_data.cc
index 3b3f17f..48c8b0f 100644
--- a/voice_engine/shared_data.cc
+++ b/voice_engine/shared_data.cc
@@ -30,8 +30,7 @@
       encoder_queue_("AudioEncoderQueue") {
   Trace::CreateTrace();
   if (TransmitMixer::Create(_transmitMixerPtr, _gInstanceCounter) == 0) {
-    _transmitMixerPtr->SetEngineInformation(*_moduleProcessThreadPtr,
-                                            _engineStatistics, _channelManager);
+    _transmitMixerPtr->SetEngineInformation(&_channelManager);
   }
 }