Optionally disable APM limiter in AudioMixer.

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 e90dac1e70e9839f032da4db4f91b8eb0d002686..f902eb6ea307c75e5c84e54258b56cc792851bc3 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl_unittest.cc
@@ -456,9 +456,10 @@ TEST(AudioMixer, UnmutedShouldMixBeforeLoud) {
 
 TEST(AudioMixer, MixingRateShouldBeDecidedByRateCalculator) {
   constexpr int kOutputRate = 22000;
-  const auto mixer = AudioMixerImpl::CreateWithOutputRateCalculator(
+  const auto mixer = AudioMixerImpl::CreateWithOutputRateCalculatorAndLimiter(
       std::unique_ptr<OutputRateCalculator>(
-          new CustomRateCalculator(kOutputRate)));
+          new CustomRateCalculator(kOutputRate)),
+      true);
   MockMixerAudioSource audio_source;
   mixer->AddSource(&audio_source);
   ResetFrame(audio_source.fake_frame());
@@ -471,9 +472,10 @@ TEST(AudioMixer, MixingRateShouldBeDecidedByRateCalculator) {
 
 TEST(AudioMixer, ZeroSourceRateShouldBeDecidedByRateCalculator) {

[ivoc, 2017/02/15 16:58:46]

Can you add a unit test that doesn't use a limiter? You can either test that it
actually doesn't limit, or alternatively just test that it works and doesn't
crash.

[aleloi, 2017/02/16 14:01:35]

Testing that it doesn't limit is pretty hard, I think. The test would have to
detect clipping in the mixed signal.

   constexpr int kOutputRate = 8000;
-  const auto mixer = AudioMixerImpl::CreateWithOutputRateCalculator(
+  const auto mixer = AudioMixerImpl::CreateWithOutputRateCalculatorAndLimiter(
       std::unique_ptr<OutputRateCalculator>(
-          new CustomRateCalculator(kOutputRate)));
+          new CustomRateCalculator(kOutputRate)),
+      true);
 
   mixer->Mix(1, &frame_for_mixing);