Add support for getting the sessionId from instrumentation and sending it to the client

pkg/analysis_server/test/integration/integration_test_methods.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.
 //
 // This file has been automatically generated.  Please do not edit it manually.
 // To regenerate the file, use the script
 // "pkg/analysis_server/tool/spec/generate_files".
 
 /**
  * Convenience methods for running integration tests
@@ skipping 74 matching lines @@
    *
    * Parameters
    *
    * version (String)
    *
    *   The version number of the analysis server.
    *
    * pid (int)
    *
    *   The process id of the analysis server process.
+   *
+   * sessionId (optional String)
+   *
+   *   The session id for this session.
    */
   Stream<ServerConnectedParams> onServerConnected;
 
   /**
    * Stream controller for [onServerConnected].
    */
   StreamController<ServerConnectedParams> _onServerConnected;
 
   /**
    * Reports that an unexpected error has occurred while executing the server.
@@ skipping 1635 matching lines @@
       case "execution.launchData":
         expect(params, isExecutionLaunchDataParams);
         _onExecutionLaunchData.add(new ExecutionLaunchDataParams.fromJson(decoder, 'params', params));
         break;
       default:
         fail('Unexpected notification: $event');
         break;
     }
   }
 }