Build Observatory as part of runtime

runtime/observatory/tests/ui/inspector.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.
 
 // See inspector.txt for expected behavior.
 
 library manual_inspector_test;
 
 import 'dart:isolate';
 import 'dart:mirrors';
@@ skipping 143 matching lines @@
   weakProperty = extractPrivateField(expando, '_data').firstWhere((e) => e != null);
 
   Isolate.spawn(secondMain, "Hello").then((otherIsolate) {
     isolate = otherIsolate;
     portSend = otherIsolate.controlPort;
     capability = otherIsolate.terminateCapability;
   });
 
   print("Finished main");
 }