Support external audio mixer.

webrtc/media/engine/webrtcvoe.h

Index: webrtc/media/engine/webrtcvoe.h
diff --git a/webrtc/media/engine/webrtcvoe.h b/webrtc/media/engine/webrtcvoe.h
index 41a5b5fe6a157a8e47dec733018e9627ab9d80c4..657d9deeb60e0acff624bcec43ced557460296ec 100644
--- a/webrtc/media/engine/webrtcvoe.h
+++ b/webrtc/media/engine/webrtcvoe.h
@@ -72,11 +72,14 @@ class scoped_voe_ptr {
 // Fake implementations can also be injected for testing.
 class VoEWrapper {
  public:
-  VoEWrapper()
-      : engine_(webrtc::VoiceEngine::Create()), processing_(engine_),
-        base_(engine_), codec_(engine_), hw_(engine_),
-        volume_(engine_) {
-  }
+  VoEWrapper(rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer)
+      : engine_(webrtc::VoiceEngine::Create()),
+        processing_(engine_),
+        base_(engine_),
+        codec_(engine_),
+        hw_(engine_),
+        volume_(engine_),
+        audio_mixer_(audio_mixer) {}
   VoEWrapper(webrtc::VoEAudioProcessing* processing,
              webrtc::VoEBase* base,
              webrtc::VoECodec* codec,
@@ -97,6 +100,9 @@ class VoEWrapper {
   webrtc::VoEHardware* hw() const { return hw_.get(); }
   webrtc::VoEVolumeControl* volume() const { return volume_.get(); }
   int error() { return base_->LastError(); }
+  rtc::scoped_refptr<webrtc::AudioMixer> AudioMixer() const {
+    return audio_mixer_;
+  }
 
  private:
   scoped_voe_engine engine_;
@@ -105,6 +111,7 @@ class VoEWrapper {
   scoped_voe_ptr<webrtc::VoECodec> codec_;
   scoped_voe_ptr<webrtc::VoEHardware> hw_;
   scoped_voe_ptr<webrtc::VoEVolumeControl> volume_;
+  rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer_ = nullptr;
 };
 }  // namespace cricket