Build Observatory as part of runtime

runtime/observatory/lib/src/elements/heap_map.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 heap_map_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:math';
 import 'observatory_element.dart';
@@ skipping 212 matching lines @@
     }).whenComplete(done);
   }
 
   void fragmentationChanged(oldValue) {
     // Async, in case attached has not yet run (observed in JS version).
     new Future(() {
       _updateFragmentationData();
     });
   }
 }