Make event renames optional, not mandatory.

lib/html/scripts/htmleventgenerator.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 functionality to generate dart:html event classes."""
 
+import logging
+
+_logger = logging.getLogger('dartgenerator')
+
 # Events without onEventName attributes in the  IDL we want to support.
 # We can automatically extract most event names by checking for
 # onEventName methods in the IDL but some events aren't listed so we need
 # to manually add them here so that they are easy for users to find.
 _html_manual_events = {
   'Element': ['touchleave', 'touchenter', 'webkitTransitionEnd'],
   'Window': ['DOMContentLoaded']
 }
 
 # These event names must be camel case when attaching event listeners
@@ skipping 205 matching lines @@
         INTERFACE=events_interface,
         SUPER='_%sImpl' % parent_events_interface)
 
     dom_event_names = set()
     for event in events:
       dom_name = event.id[2:]
       dom_name = _on_attribute_to_event_name_mapping.get(dom_name, dom_name)
       dom_event_names.add(dom_name)
     if html_interface_name in _html_manual_events:
       dom_event_names.update(_html_manual_events[html_interface_name])
-    dom_event_names = sorted(dom_event_names,
-                             key=lambda name: _html_event_names[name])
-    for dom_name in dom_event_names:
+    for dom_name in sorted(dom_event_names):
       if dom_name not in _html_event_names:
-        raise Exception('No known html even name for event: ' + dom_name)
+        _logger.warn('omitting %s event as there is no HTML name for it' % dom_name)
+        continue
+
       html_name = _html_event_names[dom_name]
       interface_events_members.Emit('\n  EventListenerList get $NAME;\n',
           NAME=html_name)
       full_event_name = '%sEvents.%s' % (html_interface_name, html_name)
       if not full_event_name in custom_events:
         implementation_events_members.Emit(
             "\n"
             "  EventListenerList get $NAME => this['$DOM_NAME'];\n",
             NAME=html_name,
             DOM_NAME=dom_name)
 
     return events_interface
 
   # TODO(jacobr): this isn't quite right....
   def _GetParentEventsInterface(self, interface):
     # Ugly hack as we don't specify that Document and DocumentFragment inherit
     # from Element in our IDL.
     if interface.id == 'Document' or interface.id == 'DocumentFragment':
       return 'ElementEvents'
 
     parent_events_interface = 'Events'
     interfaces_with_events = set()
     for parent in self._database.Hierarchy(interface):
       if parent != interface and parent.id in self._event_classes:
         parent_events_interface = parent.id + 'Events'
         interfaces_with_events.add(parent)
     if len(interfaces_with_events) > 1:
       raise Exception('Only one parent event class allowed ' + interface.id)
     return parent_events_interface