Don't link with audio codecs that we don't use

webrtc/modules/audio_coding/main/acm2/codec_owner.cc

Index: webrtc/modules/audio_coding/main/acm2/codec_owner.cc
diff --git a/webrtc/modules/audio_coding/main/acm2/codec_owner.cc b/webrtc/modules/audio_coding/main/acm2/codec_owner.cc
index 669eadb68e87452810411fee1a3ddeb16344b5c2..66be85ff8e333f74668f0a9c7946bd386f282884 100644
--- a/webrtc/modules/audio_coding/main/acm2/codec_owner.cc
+++ b/webrtc/modules/audio_coding/main/acm2/codec_owner.cc
@@ -131,15 +131,18 @@ rtc::scoped_ptr<AudioEncoder> CreateSpeechEncoder(
 AudioEncoder* CreateRedEncoder(int red_payload_type,
                                AudioEncoder* encoder,
                                rtc::scoped_ptr<AudioEncoder>* red_encoder) {
-  if (red_payload_type == -1) {
-    red_encoder->reset();
-    return encoder;
+#ifdef WEBRTC_CODEC_RED
+  if (red_payload_type != -1) {
+    AudioEncoderCopyRed::Config config;
+    config.payload_type = red_payload_type;
+    config.speech_encoder = encoder;
+    red_encoder->reset(new AudioEncoderCopyRed(config));
+    return red_encoder->get();
   }
-  AudioEncoderCopyRed::Config config;
-  config.payload_type = red_payload_type;
-  config.speech_encoder = encoder;
-  red_encoder->reset(new AudioEncoderCopyRed(config));
-  return red_encoder->get();
+#endif
+
+  red_encoder->reset();
+  return encoder;
 }
 
 void CreateCngEncoder(int cng_payload_type,