Build Observatory as part of runtime

runtime/observatory/lib/service_common.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 service_common;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';
 
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           'query': request.id
         }
       });
     } else {
       message = JSON.encode({'seq': serial, 'request': request.id});
     }
     // Send message.
     _webSocket.send(message);
   }
 }