Second layer of mixing for audio elements.

content/renderer/media/audio_renderer_mixer_manager_unittest.cc

Index: content/renderer/media/audio_renderer_mixer_manager_unittest.cc
diff --git a/content/renderer/media/audio_renderer_mixer_manager_unittest.cc b/content/renderer/media/audio_renderer_mixer_manager_unittest.cc
index fd776bde2b6491b4125c98aae2e7e12c828eadcb..bfc0f9f0d01785cffaebdafd872d75102853882c 100644
--- a/content/renderer/media/audio_renderer_mixer_manager_unittest.cc
+++ b/content/renderer/media/audio_renderer_mixer_manager_unittest.cc
@@ -22,6 +22,8 @@ static const int kBitsPerChannel = 16;
 static const int kSampleRate = 48000;
 static const int kBufferSize = 8192;
 static const media::ChannelLayout kChannelLayout = media::CHANNEL_LAYOUT_STEREO;
+static const media::ChannelLayout kAnotherChannelLayout =
+    media::CHANNEL_LAYOUT_2_1;
 static const std::string kDefaultDeviceId;
 static const url::Origin kSecurityOrigin;
 
@@ -108,7 +110,7 @@ TEST_F(AudioRendererMixerManagerTest, GetRemoveMixer) {
   EXPECT_EQ(mixer_count(), 1);
 
   media::AudioParameters params2(
-      AudioParameters::AUDIO_PCM_LINEAR, kChannelLayout, kSampleRate * 2,
+      AudioParameters::AUDIO_PCM_LINEAR, kAnotherChannelLayout, kSampleRate * 2,
       kBitsPerChannel, kBufferSize * 2);
   media::AudioRendererMixer* mixer2 = GetMixer(
       kRenderFrameId, params2, kDefaultDeviceId, kSecurityOrigin, nullptr);
@@ -142,21 +144,25 @@ TEST_F(AudioRendererMixerManagerTest, MixerReuse) {
   ASSERT_TRUE(mixer1);
   EXPECT_EQ(mixer_count(), 1);
 
-  // Different formats, bit depths, and buffer sizes should not result in a
-  // different mixer.
+  // Different sample rates, formats, bit depths, and buffer sizes should not
+  // result in a different mixer.
   media::AudioParameters params2(AudioParameters::AUDIO_PCM_LOW_LATENCY,
-                                 kChannelLayout, kSampleRate,
-                                 kBitsPerChannel * 2, kBufferSize * 2);
+                                 kChannelLayout,
+                                 kSampleRate * 2,
+                                 kBitsPerChannel * 2,
+                                 kBufferSize * 2);
   EXPECT_EQ(mixer1, GetMixer(kRenderFrameId, params2, kDefaultDeviceId,
                              kSecurityOrigin, nullptr));
   EXPECT_EQ(mixer_count(), 1);
   RemoveMixer(kRenderFrameId, params2, kDefaultDeviceId, kSecurityOrigin);
   EXPECT_EQ(mixer_count(), 1);
 
-  // Modify some parameters that do matter.
+  // Modify some parameters that do matter: channel layout
   media::AudioParameters params3(AudioParameters::AUDIO_PCM_LOW_LATENCY,
-                                 media::CHANNEL_LAYOUT_MONO, kSampleRate * 2,
-                                 kBitsPerChannel, kBufferSize);
+                                 kAnotherChannelLayout,
+                                 kSampleRate,
+                                 kBitsPerChannel,
+                                 kBufferSize);
   ASSERT_NE(params3.channel_layout(), params1.channel_layout());
 
   EXPECT_NE(mixer1, GetMixer(kRenderFrameId, params3, kDefaultDeviceId,