Fixing dart2js codesize regression from blink roll.

tools/dom/scripts/dartmetadata.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 to provide Dart metadata for
 DOM APIs.
 """
 
 import copy
@@ skipping 65 matching lines @@
     ],
 
     'Window.openDatabase': [
       "@Creates('SqlDatabase')",
     ],
 
     'Window.showModalDialog': [
       "@Creates('Null')",
     ],
 
+    "ErrorEvent.error": [
+      "@Creates('Null')", # Only returns values created elsewhere.
+    ],
+
     # To be in callback with the browser-created Event, we had to have called
     # addEventListener on the target, so we avoid
     'Event.currentTarget': [
       "@Creates('Null')",
       "@Returns('EventTarget|=Object')",
     ],
 
     # Only nodes in the DOM bubble and have target !== currentTarget.
     'Event.target': [
       "@Creates('Node')",
@@ skipping 656 matching lines @@
       pass
     else:
       _logger.warn('Unknown support_level - %s:%s' % (interface_id, member_id))
 
     return annotations
 
   def Flush(self):
     json_file = open(self._api_status_path, 'w+')
     json.dump(self._types, json_file, indent=2, separators=(',', ': '), sort_keys=True)
     json_file.close()