Build Observatory as part of runtime

runtime/observatory/test/graph_test.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.
 
 import 'dart:async';
 import 'package:observatory/object_graph.dart';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
@@ skipping 78 matching lines @@
     Class fooClass = lib.classes.first;
     fooId = fooClass.vmCid;
     isolate.get('graph');
     return completer.future;
   });
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);