Build Observatory as part of runtime

runtime/observatory/lib/src/elements/metrics.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 metrics;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:observatory/app.dart';
@@ skipping 179 matching lines @@
       _table.addTimeOfDayValue(sample.time, sample.value);
     }
   }
 
   metricChanged(oldValue) {
     if (oldValue != metric) {
       _setupInitialDataTable();
     }
   }
 }