Build Observatory as part of runtime

runtime/observatory/lib/src/elements/observatory_element.dart

 // Copyright (c) 2013, 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 observatory_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'package:observatory/app.dart';
 import 'package:polymer/polymer.dart';
@@ skipping 120 matching lines @@
       } else result.add(codeUnit);
     }
     if (wasTruncated) {
       result.addAll("...".codeUnits);
     } else {
       result.add("'".codeUnitAt(0));
     }
     return new String.fromCharCodes(result);
   }
 }