Add the function NewMessage to popup the compose window.

mailnews/ui/messenger/resources/mailshell.xul

@@ -98,6 +98,17 @@ function OpenURL(url)
    }
 }
 
+function NewMessage()
+{
+	dump("\n\nnewMsg from XUL\n\n\n");
+	var appCore = new ComposeAppCore();
+	if (appCore != null) {
+		dump("Initializing ComposeAppCore and creating a new Message\n");
+		appCore.Init("ComposeAppCore");
+		appCore.NewMessage("resource:/res/samples/compose.xul");
+	}
+}
+
 </html:script>
 
   <menubar>