Fix a few strong mode errors in dart:html

tools/dom/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
 import monitored
 
@@ skipping 105 matching lines @@
   '*.wheel': ('wheel', 'WheelEvent'),
   'AbstractWorker.error': ('error', 'ErrorEvent'),
   'AudioContext.complete': ('complete', 'Event'),
   'ApplicationCache.cached': ('cached', 'Event'),
   'ApplicationCache.checking': ('checking', 'Event'),
   'ApplicationCache.downloading': ('downloading', 'Event'),
   'ApplicationCache.noupdate': ('noUpdate', 'Event'),
   'ApplicationCache.obsolete': ('obsolete', 'Event'),
   'ApplicationCache.progress': ('progress', 'ProgressEvent'),
   'ApplicationCache.updateready': ('updateReady', 'Event'),
+  'CompositorWorker.error': ('error', 'ErrorEvent'),
   'Document.readystatechange': ('readyStateChange', 'Event'),
   'Document.securitypolicyviolation': ('securityPolicyViolation', 'SecurityPolicyViolationEvent'),
   'Document.selectionchange': ('selectionChange', 'Event'),
   'Document.pointerlockchange': ('pointerLockChange', 'Event'),
   'Document.pointerlockerror': ('pointerLockError', 'Event'),
   'EventSource.open': ('open', 'Event'),
   'FileReader.abort': ('abort', 'ProgressEvent'),
   'FileReader.load': ('load', 'ProgressEvent'),
   'FileReader.loadend': ('loadEnd', 'ProgressEvent'),
   'FileReader.loadstart': ('loadStart', 'ProgressEvent'),
@@ skipping 47 matching lines @@
   'RTCDataChannel.close': ('close', 'Event'),
   'RTCDataChannel.open': ('open', 'Event'),
   'RTCPeerConnection.addstream': ('addStream', 'MediaStreamEvent'),
   'RTCPeerConnection.datachannel': ('dataChannel', 'RtcDataChannelEvent'),
   'RTCPeerConnection.icecandidate': ('iceCandidate', 'RtcIceCandidateEvent'),
   'RTCPeerConnection.iceconnectionstatechange': ('iceConnectionStateChange', 'Event'),
   'RTCPeerConnection.negotiationneeded': ('negotiationNeeded', 'Event'),
   'RTCPeerConnection.removestream': ('removeStream', 'MediaStreamEvent'),
   'RTCPeerConnection.signalingstatechange': ('signalingStateChange', 'Event'),
   'ScriptProcessorNode.audioprocess': ('audioProcess', 'AudioProcessingEvent'),
+  'SharedWorker.error': ('error', 'ErrorEvent'),
   'SharedWorkerGlobalScope.connect': ('connect', 'Event'),
   'SpeechRecognition.audioend': ('audioEnd', 'Event'),
   'SpeechRecognition.audiostart': ('audioStart', 'Event'),
   'SpeechRecognition.end': ('end', 'Event'),
   'SpeechRecognition.error': ('error', 'SpeechRecognitionError'),
   'SpeechRecognition.nomatch': ('noMatch', 'SpeechRecognitionEvent'),
   'SpeechRecognition.result': ('result', 'SpeechRecognitionEvent'),
   'SpeechRecognition.soundend': ('soundEnd', 'Event'),
   'SpeechRecognition.soundstart': ('soundStart', 'Event'),
   'SpeechRecognition.speechend': ('speechEnd', 'Event'),
@@ skipping 11 matching lines @@
   'WebSocket.close': ('close', 'CloseEvent'),
   'WebSocket.open': ('open', 'Event'), # should be OpenEvent, but not exposed.
   'Window.DOMContentLoaded': ('contentLoaded', 'Event'),
   'Window.devicemotion': ('deviceMotion', 'DeviceMotionEvent'),
   'Window.deviceorientation': ('deviceOrientation', 'DeviceOrientationEvent'),
   'Window.loadstart': ('loadStart', 'Event'),
   'Window.pagehide': ('pageHide', 'Event'),
   'Window.pageshow': ('pageShow', 'Event'),
   'Window.progress': ('progress', 'Event'),
   'Window.webkittransitionend': ('webkitTransitionEnd', 'TransitionEvent'),
+  'Worker.error': ('error', 'ErrorEvent'),
   'XMLHttpRequestEventTarget.abort': ('abort', 'ProgressEvent'),
   'XMLHttpRequestEventTarget.error': ('error', 'ProgressEvent'),
   'XMLHttpRequestEventTarget.load': ('load', 'ProgressEvent'),
   'XMLHttpRequestEventTarget.loadend': ('loadEnd', 'ProgressEvent'),
   'XMLHttpRequestEventTarget.loadstart': ('loadStart', 'ProgressEvent'),
   'XMLHttpRequestEventTarget.progress': ('progress', 'ProgressEvent'),
   'XMLHttpRequestEventTarget.timeout': ('timeout', 'ProgressEvent'),
   'XMLHttpRequest.readystatechange': ('readyStateChange', 'ProgressEvent'),
 })
 
@@ skipping 176 matching lines @@
     """
     key = '%s.%s' % (html_interface_name, dom_event_name)
     if key in _html_event_types:
       return _html_event_types[key]
     key = '*.%s' % dom_event_name
     if key in _html_event_types:
       return _html_event_types[key]
     _logger.warn('Cannot resolve event type for %s.%s' %
         (html_interface_name, dom_event_name))
     return None