Improve performance of table trees by around 3x

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 70 matching lines @@
       return;
     }
     // Restart timer.
     _pollTimer = new Timer(pollPeriod, _onPoll);
   }
 
   /// Utility method for handling on-click of <a> tags. Navigates
   /// within the application using the [LocationManager].
   void goto(MouseEvent event, var detail, Element target) {
     app.locationManager.onGoto(event, detail, target);
+    event.stopPropagation();
   }
 
   /// Create a link that can be consumed by [goto].
   String gotoLink(String url) {
     return app.locationManager.makeLink(url);
   }
 
   String formatTimePrecise(double time) => Utils.formatTimePrecise(time);
 
   String formatTime(double time) => Utils.formatTime(time);
@@ skipping 30 matching lines @@
       } else result.add(codeUnit);
     }
     if (wasTruncated) {
       result.addAll("...".codeUnits);
     } else {
       result.add("'".codeUnitAt(0));
     }
     return new String.fromCharCodes(result);
   }
 }