Events operator [] shouldn't convert event name to lower case.

lib/dom/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."""
 
 from systemfrog import *
 from systeminterface import *
@@ skipping 1202 matching lines @@
         '  $CLASSNAME(_ptr) : super(_ptr);\n'
         '$!MEMBERS}\n',
         CLASSNAME=events_class,
         INTERFACE=events_interface,
         SUPER='_' + parent_event_class + 'Impl')
 
     for event_name in event_attrs:
       if event_name in _html_event_names:
         events_members.Emit(
             "\n"
-            "  EventListenerList get $NAME() => _get('$RAWNAME');\n",
+            "  EventListenerList get $NAME() => this['$RAWNAME'];\n",
             RAWNAME=event_name,
             NAME=_html_event_names[event_name])
       else:
         raise Exception('No known html even name for event: ' + event_name)
 
   def _EmitEventGetter(self, events_class):
     self._members_emitter.Emit(
         '\n  $TYPE get on() =>\n    new $TYPE(this);\n',
         TYPE=events_class)
 
@@ skipping 459 matching lines @@
             Collect(database.GetInterface(parent.type.id),
                     seen, collected)
 
   inheritance_closure = {}
   for interface in database.GetInterfaces():
     seen = set()
     collected = []
     Collect(interface, seen, collected)
     inheritance_closure[interface.id] = collected
   return inheritance_closure