Build Observatory as part of runtime

runtime/observatory/lib/src/elements/eval_box.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 eval_box_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:polymer/polymer.dart';
@@ skipping 37 matching lines @@
   }
 
   void selectExpr(MouseEvent e) {
     assert(e.target is Element);
     Element targetElement = e.target;
     text = targetElement.getAttribute('expr');
   }
 
   EvalBoxElement.created() : super.created();
 }