Moved MixerAudioSource and removed audio_mixer_defines.h.

webrtc/modules/audio_mixer/audio_source_with_mix_status.cc

Index: webrtc/modules/audio_mixer/audio_source_with_mix_status.cc
diff --git a/webrtc/modules/audio_mixer/audio_source_with_mix_status.cc b/webrtc/modules/audio_mixer/audio_source_with_mix_status.cc
index 40ccad4ad7d72e8e0a9f191dbb91ea8b53dd4718..db94887ad932d475854b9f38bbb485f558ed3eb1 100644
--- a/webrtc/modules/audio_mixer/audio_source_with_mix_status.cc
+++ b/webrtc/modules/audio_mixer/audio_source_with_mix_status.cc
@@ -13,7 +13,7 @@
 namespace webrtc {
 
 AudioSourceWithMixStatus::AudioSourceWithMixStatus(
-    MixerAudioSource* audio_source)
+    AudioMixer::Source* audio_source)
     : audio_source_(audio_source) {}
 
 AudioSourceWithMixStatus::~AudioSourceWithMixStatus() {}
@@ -36,7 +36,7 @@ void AudioSourceWithMixStatus::ResetMixedStatus() {
   is_mixed_ = false;
 }
 
-MixerAudioSource* AudioSourceWithMixStatus::audio_source() const {
+AudioMixer::Source* AudioSourceWithMixStatus::audio_source() const {
   return audio_source_;
 }