Revert of Storing raw audio sink for default audio track.

talk/media/base/fakemediaengine.h

Index: talk/media/base/fakemediaengine.h
diff --git a/talk/media/base/fakemediaengine.h b/talk/media/base/fakemediaengine.h
index 5f7f3ef3cb9a1315ef21492e413648aaf4400e6e..f5b21741d36778c5ded15a1e78226e7b5b599827 100644
--- a/talk/media/base/fakemediaengine.h
+++ b/talk/media/base/fakemediaengine.h
@@ -349,8 +349,8 @@
 
   virtual void SetRawAudioSink(
       uint32_t ssrc,
-      const rtc::scoped_refptr<webrtc::AudioSinkInterface>& sink) {
-    sink_ = sink;
+      rtc::scoped_ptr<webrtc::AudioSinkInterface> sink) {
+    sink_ = std::move(sink);
   }
 
  private:
@@ -425,7 +425,7 @@
   int time_since_last_typing_;
   AudioOptions options_;
   std::map<uint32_t, VoiceChannelAudioSink*> local_renderers_;
-  rtc::scoped_refptr<webrtc::AudioSinkInterface> sink_;
+  rtc::scoped_ptr<webrtc::AudioSinkInterface> sink_;
 };
 
 // A helper function to compare the FakeVoiceMediaChannel::DtmfInfo.