Let AudioCodingModule::SendCodec return Maybe<CodecInst>

And deal with the consequences thereof...

Review URL: https://codereview.webrtc.org/1406123011

Cr-Commit-Position: refs/heads/master@{#10497}
diff --git a/webrtc/modules/audio_coding/main/test/TestAllCodecs.cc b/webrtc/modules/audio_coding/main/test/TestAllCodecs.cc
index 19189b6..e9e4f2b 100644
--- a/webrtc/modules/audio_coding/main/test/TestAllCodecs.cc
+++ b/webrtc/modules/audio_coding/main/test/TestAllCodecs.cc
@@ -477,8 +477,7 @@
 
 void TestAllCodecs::DisplaySendReceiveCodec() {
   CodecInst my_codec_param;
-  acm_a_->SendCodec(&my_codec_param);
-  printf("%s -> ", my_codec_param.plname);
+  printf("%s -> ", acm_a_->SendCodec()->plname);
   acm_b_->ReceiveCodec(&my_codec_param);
   printf("%s\n", my_codec_param.plname);
 }