Simplifications of the mixing algorithm.

webrtc/modules/audio_mixer/test/audio_mixer_unittest.cc

Index: webrtc/modules/audio_mixer/test/audio_mixer_unittest.cc
diff --git a/webrtc/modules/audio_mixer/test/audio_mixer_unittest.cc b/webrtc/modules/audio_mixer/test/audio_mixer_unittest.cc
index fd639f226cfb545a7c0446dcb06848c4493216f9..bfc00fd32dc79985df3c3fa41091e57989286458 100644
--- a/webrtc/modules/audio_mixer/test/audio_mixer_unittest.cc
+++ b/webrtc/modules/audio_mixer/test/audio_mixer_unittest.cc
@@ -271,6 +271,8 @@ TEST(AudioMixer, ParticipantSampleRate) {
   for (auto frequency : {8000, 16000, 32000, 48000}) {
     EXPECT_CALL(participant, GetAudioFrameWithMuted(_, frequency))
         .Times(Exactly(1));
+    participant.fake_frame()->sample_rate_hz_ = frequency;
+    participant.fake_frame()->samples_per_channel_ = frequency / 100;
     mixer->Mix(frequency, 1, &frame_for_mixing);
     EXPECT_EQ(frequency, frame_for_mixing.sample_rate_hz_);
   }