close channel and exit analysis server on editor shutdown

pkg/analysis_server/lib/driver.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library driver;
 
 import 'dart:io';
 
 import 'package:analysis_server/http_server.dart';
 import 'package:analysis_server/src/socket_server.dart';
@@ skipping 64 matching lines @@
       }
     }
 
     if (serve_http) {
       httpServer.serveHttp(port);
     }
     stdioServer.serveStdio().then((_) {
       if (serve_http) {
         httpServer.close();
       }
+      exit(0);
     });
   }
 
   /**
    * Print information about how to use the server.
    */
   void _printUsage(ArgParser parser) {
     print('Usage: $BINARY_NAME [flags]');
     print('');
     print('Supported flags are:');
     print(parser.getUsage());
   }
 }