Bug 1299324: return error if an audio channel is already open until multi-mic support is done r=jib

dom/media/webrtc/MediaEngineWebRTCAudio.cpp

@@ -298,6 +298,10 @@ MediaEngineWebRTCMicrophoneSource::UpdateSingleSource(
           LOG(("Audio engine is not initalized"));
           return NS_ERROR_FAILURE;
         }
+      } else {
+        // Until we fix (or wallpaper) support for multiple mic input
+        // (Bug 1238038) fail allocation for a second device
+        return NS_ERROR_FAILURE;
       }
       if (!AllocChannel()) {
         LOG(("Audio device is not initalized"));