Add another event name.

lib/html/scripts/systemhtml.py

 #!/usr/bin/python
 # Copyright (c) 2012, 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 module provides shared functionality for the system to generate
 Dart:html APIs from the IDL database."""
 
 import emitter
 
@@ skipping 121 matching lines @@
   'loadend': 'loadEnd',
   'loadstart': 'loadStart',
   'message': 'message',
   'mousedown': 'mouseDown',
   'mousemove': 'mouseMove',
   'mouseout': 'mouseOut',
   'mouseover': 'mouseOver',
   'mouseup': 'mouseUp',
   'mousewheel': 'mouseWheel',
   'mute': 'mute',
+  'negotationneeded': 'negotationNeeded',
   'nomatch': 'noMatch',
   'noupdate': 'noUpdate',
   'obsolete': 'obsolete',
   'offline': 'offline',
   'online': 'online',
   'open': 'open',
   'pagehide': 'pageHide',
   'pageshow': 'pageShow',
   'paste': 'paste',
   'pause': 'pause',
@@ skipping 1081 matching lines @@
     return HtmlDart2JSClassGenerator(self, interface)
 
   def GenerateLibraries(self, dart_files):
     self._GenerateLibFile(
         'html_dart2js.darttemplate',
         os.path.join(self._output_dir, 'html_dart2js.dart'),
         dart_files)
 
   def Finish(self):
     pass