Posting Opus's set-force-channels functionality to WebRTC.

webrtc/modules/audio_coding/codecs/opus/opus_unittest.cc

Index: webrtc/modules/audio_coding/codecs/opus/opus_unittest.cc
diff --git a/webrtc/modules/audio_coding/codecs/opus/opus_unittest.cc b/webrtc/modules/audio_coding/codecs/opus/opus_unittest.cc
index c634885e525b1de8086d6d592438375786596423..84b27979b278a6c8b7987004d867699436268686 100644
--- a/webrtc/modules/audio_coding/codecs/opus/opus_unittest.cc
+++ b/webrtc/modules/audio_coding/codecs/opus/opus_unittest.cc
@@ -409,6 +409,27 @@ TEST_P(OpusTest, OpusSetComplexity) {
   EXPECT_EQ(0, WebRtcOpus_EncoderFree(opus_encoder_));
 }
 
+TEST_P(OpusTest, OpusForceChannels) {
+  // Test without creating encoder memory.
+  EXPECT_EQ(-1, WebRtcOpus_SetForceChannels(opus_encoder_, 1));
+
+  ASSERT_EQ(0,
+            WebRtcOpus_EncoderCreate(&opus_encoder_, channels_, application_));
+
+  if (channels_ == 2) {
+    EXPECT_EQ(-1, WebRtcOpus_SetForceChannels(opus_encoder_, 3));
+    EXPECT_EQ(0, WebRtcOpus_SetForceChannels(opus_encoder_, 2));
+    EXPECT_EQ(0, WebRtcOpus_SetForceChannels(opus_encoder_, 1));
+    EXPECT_EQ(0, WebRtcOpus_SetForceChannels(opus_encoder_, 0));
+  } else {
+    EXPECT_EQ(-1, WebRtcOpus_SetForceChannels(opus_encoder_, 2));
+    EXPECT_EQ(0, WebRtcOpus_SetForceChannels(opus_encoder_, 1));
+    EXPECT_EQ(0, WebRtcOpus_SetForceChannels(opus_encoder_, 0));
+  }
+
+  EXPECT_EQ(0, WebRtcOpus_EncoderFree(opus_encoder_));
+}
+
 // Encode and decode one frame, initialize the decoder and
 // decode once more.
 TEST_P(OpusTest, OpusDecodeInit) {