Add support for asynchronous event notification to the observatory.

runtime/bin/vmservice/client/lib/src/elements/script_inset.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 script_inset_element;
 
 import 'observatory_element.dart';
 import 'package:observatory/service.dart';
 import 'package:polymer/polymer.dart';
 
@@ skipping 54 matching lines @@
         if (script.loaded) {
           _updateFuture = null;
           _updateLines();
         }
       });
       return;
     }
     startLine =
         (pos != null) ? script.tokenToLine(pos) - 1 : 0;
     endLine =
-        (endPos != null) ? script.tokenToLine(endPos) : script.lines.length;
+        (endPos != null) ? script.tokenToLine(endPos) : startLine + 1;
     // Add line numbers.
     lineNumbers.clear();
     for (var i = startLine; i < endLine; i++) {
       lineNumbers.add(i);
     }
   }
 
   ScriptInsetElement.created() : super.created();
 }