Add LayoutTestController.display method.

lib/dom/src/native_DOMPublic.dart

 // Copyright (c) 2011, 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.
 
 // This API is exploratory.
 spawnDomIsolateImpl(Window targetWindow, String entryPoint) {
   if (targetWindow is! DOMWindowImplementation && targetWindow is! DOMWindowCrossFrameImplementation) {
     throw 'Bad window argument: $targetWindow';
   }
   final result = new Completer<SendPort>();
@@ skipping 11 matching lines @@
   if (_layoutTestController === null)
     _layoutTestController = new LayoutTestController._(NPObject.retrieve("layoutTestController"));
   return _layoutTestController;
 }
 
 class LayoutTestController {
   final NPObject _npObject;
 
   LayoutTestController._(this._npObject);
 
+  display() => _npObject.invoke('display');
   dumpAsText() => _npObject.invoke('dumpAsText');
   notifyDone() => _npObject.invoke('notifyDone');
   setCanOpenWindows() => _npObject.invoke('setCanOpenWindows');
   waitUntilDone() => _npObject.invoke('waitUntilDone');
 }