[Chat] add skeleton for sound

Chat/Chat/ChatViewController.cs

@@ -6,6 +6,7 @@ using UIKit;
 using Foundation;
 using CoreGraphics;
 using ObjCRuntime;
+using AudioToolbox;
 
 namespace Chat
 {
@@ -15,6 +16,8 @@ namespace Chat
 		NSObject willHideToken;
 		NSObject willHideMenuToken;
 
+		SystemSound sentSound;
+
 		List<Message> messages;
 		ChatSource chatSrc;
 
@@ -325,6 +328,11 @@ namespace Chat
 			var selected = TableView.IndexPathForSelectedRow;
 			TableView.DeselectRow (selected, false);
 		}
+
+		void PlayMessageSentSound()
+		{
+			throw new NotImplementedException ();
+		}
 	}
 
 	public class DummyInput : UITextView