Adding SetOpusMaxBandwidth in VoE and ACM

This is a step to solve
https://code.google.com/p/webrtc/issues/detail?id=1906

In particular, we add an API in VoE and ACM to call Opus's API of setting maximum bandwidth.

TEST = added a test in voe_cmd_test and listened to the result

BUG=
R=henrika@google.com, henrika@webrtc.org, turaj@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/21129004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@6869 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/voice_engine/channel.cc b/voice_engine/channel.cc
index c9364ef..3f13ba2 100644
--- a/voice_engine/channel.cc
+++ b/voice_engine/channel.cc
@@ -1749,6 +1749,19 @@
     return 0;
 }
 
+int Channel::SetOpusMaxBandwidth(int bandwidth_hz) {
+  WEBRTC_TRACE(kTraceInfo, kTraceVoice, VoEId(_instanceId, _channelId),
+               "Channel::SetOpusMaxBandwidth()");
+
+  if (audio_coding_->SetOpusMaxBandwidth(bandwidth_hz) != 0) {
+    _engineStatisticsPtr->SetLastError(
+        VE_AUDIO_CODING_MODULE_ERROR, kTraceError,
+        "SetOpusMaxBandwidth() failed to set maximum encoding bandwidth");
+    return -1;
+  }
+  return 0;
+}
+
 int32_t Channel::RegisterExternalTransport(Transport& transport)
 {
     WEBRTC_TRACE(kTraceInfo, kTraceVoice, VoEId(_instanceId, _channelId),