Split audio mixer into interface and implementation.

webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc

Index: webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc b/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
index 1e5f1fee954d8ed2a1298bd78496fdc8bd99d560..9147a15000b8ee6d1124f155a5432ba07634a269 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
@@ -14,10 +14,10 @@
 #include <memory>
 #include <utility>
 
+#include "webrtc/api/audio/audio_mixer.h"
 #include "webrtc/base/bind.h"
 #include "webrtc/base/thread.h"
 #include "webrtc/modules/audio_mixer/audio_mixer_impl.h"
-#include "webrtc/modules/audio_mixer/audio_mixer.h"
 #include "webrtc/test/gmock.h"
 
 using testing::_;
@@ -60,7 +60,7 @@ class MockMixerAudioSource : public AudioMixer::Source {
 
   MOCK_METHOD1(GetAudioFrameWithInfo, AudioFrameWithInfo(int sample_rate_hz));
 
-  MOCK_METHOD0(ssrc, int());
+  MOCK_METHOD0(Ssrc, int());
 
   AudioFrame* fake_frame() { return &fake_frame_; }
   AudioFrameInfo fake_info() { return fake_audio_frame_info_; }