Made MixerAudioSource a pure interface.

webrtc/modules/audio_mixer/audio_mixer_impl.h

Index: webrtc/modules/audio_mixer/audio_mixer_impl.h
diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl.h b/webrtc/modules/audio_mixer/audio_mixer_impl.h
index ecfcbfa621d1d2213c719a23cc1331d90237c0b8..409dcc91f32014153bfe274535116dd1e380a620 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl.h
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl.h
@@ -15,11 +15,13 @@
 #include <memory>
 #include <vector>
 
+#include "webrtc/base/gtest_prod_util.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/base/thread_checker.h"
 #include "webrtc/engine_configurations.h"
 #include "webrtc/modules/audio_mixer/audio_mixer.h"
 #include "webrtc/modules/audio_mixer/audio_mixer_defines.h"
+#include "webrtc/modules/audio_mixer/audio_source_with_mix_status.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/system_wrappers/include/critical_section_wrapper.h"
@@ -28,14 +30,14 @@
 namespace webrtc {
 
 typedef std::vector<AudioFrame*> AudioFrameList;
-typedef std::vector<MixerAudioSource*> MixerAudioSourceList;
+typedef std::vector<AudioSourceWithMixStatus> MixerAudioSourceList;
 
 class AudioMixerImpl : public AudioMixer {
  public:
   // AudioProcessing only accepts 10 ms frames.
   static const int kFrameDurationInMs = 10;
 
-  static std::unique_ptr<AudioMixer> Create(int id);
+  static std::unique_ptr<AudioMixerImpl> Create(int id);

[ivoc, 2016/10/04 20:39:29]

Don't you need the old Create function as well?

[aleloi, 2016/10/05 15:18:19]

There are two Create functions defined in the impl.cc file: 
std::unique_ptr<AudioMixer> AudioMixer::Create
std::unique_ptr<AudioMixerImpl> AudioMixerImpl::Create

Both are currently needed, but the latest redesign plan will move the first one
somewhere else and rename it into something like 

std::unique_ptr<AudioMixer> Something::CreateTop3Mixer

 
   ~AudioMixerImpl() override;
 
@@ -51,6 +53,11 @@ class AudioMixerImpl : public AudioMixer {
   bool AnonymousMixabilityStatus(
       const MixerAudioSource& audio_source) const override;
 
+  // Returns true if the participant was mixed last round. Returns
+  // false and logs an error if the participant was never added to the
+  // mixer.
+  bool GetAudioSourceMixabilityStatus(MixerAudioSource* participant);

[the sun, 2016/10/04 20:36:10]

Source or participant? Make thy mind up! :)

[aleloi, 2016/10/05 15:18:19]

Done.

+
  private:
   AudioMixerImpl(int id, std::unique_ptr<AudioProcessing> limiter);
 
@@ -61,11 +68,11 @@ class AudioMixerImpl : public AudioMixer {
   // Compute what audio sources to mix from audio_source_list_. Ramp
   // in and out. Update mixed status. Mixes up to
   // kMaximumAmountOfMixedAudioSources audio sources.
-  AudioFrameList GetNonAnonymousAudio() const EXCLUSIVE_LOCKS_REQUIRED(crit_);
+  AudioFrameList GetNonAnonymousAudio() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   // Return the AudioFrames that should be mixed anonymously. Ramp in
   // and out. Update mixed status.
-  AudioFrameList GetAnonymousAudio() const EXCLUSIVE_LOCKS_REQUIRED(crit_);
+  AudioFrameList GetAnonymousAudio() EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   // This function returns true if it finds the MixerAudioSource in the
   // specified list of MixerAudioSources.
@@ -86,6 +93,11 @@ class AudioMixerImpl : public AudioMixer {
 
   int GetOutputAudioLevelFullRange() override;
 
+  // Searches for the AudioSourceWithMixStatus object corresponding to
+  // an audio source. If the audio source was never added with
+  // Set*MixabilityStatus, this returns nullptr.
+  AudioSourceWithMixStatus* GetSourceWithStatus(MixerAudioSource* audio_source);
+
   rtc::CriticalSection crit_;
 
   const int32_t id_;
@@ -117,6 +129,7 @@ class AudioMixerImpl : public AudioMixer {
   voe::AudioLevel audio_level_ ACCESS_ON(&thread_checker_);
 
   RTC_DISALLOW_COPY_AND_ASSIGN(AudioMixerImpl);
+  FRIEND_TEST_ALL_PREFIXES(AudioMixerTest, Create);

[the sun, 2016/10/04 20:36:10]

Can we test without creating a circular relationship between the mixer impl and
the test cases? Please?

[aleloi, 2016/10/05 15:18:19]

MixerImpl::Create is public now. When we split the mixer build targets into API
+ implementation, we can make the tests depend on the implementation. Then it
should be possible to get a gn check warning if some other target includes
audio_mixer_impl.

[the sun, 2016/10/05 19:32:11]

I don't understand. Why can't we make the test depend on the impl already now?

Declaring a test as a friend of the class being tested tells me something is
wrong...

[aleloi, 2016/10/06 09:26:12]

That was confusing, sorry. We can depend only on the implementation now (which
we do in the patch that removes 'friend'). When we split the build target into
api + impl, that dependency can be done more explicit and the build system will
issue warnings when someone includes the impl.h  file.

 };
 }  // namespace webrtc