Allow null strings in setters.

tools/dom/scripts/systemnative.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 systems to generate
 native binding from the IDL database."""
 
 import emitter
 import os
 from generator import *
 from htmldartgenerator import *
-from idlnode import IDLArgument
+from idlnode import IDLArgument, IDLAttribute
 from systemhtml import js_support_checks, GetCallbackInfo, HTML_LIBRARY_NAMES
 
 _cpp_type_map = {
   ('DataTransferItem', 'webkitGetAsEntry'): 'DataTransferItemFileSystem',
   ('DOMWindow', 'indexedDB'): 'DOMWindowIndexedDatabase',
   ('DOMWindow', 'speechSynthesis'): 'DOMWindowSpeechSynthesis',
   ('DOMWindow', 'webkitNotifications'): 'DOMWindowNotifications',
   ('DOMWindow', 'storage'): 'DOMWindowQuota',
   ('DOMWindow', 'webkitStorageInfo'): 'DOMWindowQuota',
   ('DOMWindow', 'openDatabase'): 'DOMWindowWebDatabase',
@@ skipping 767 matching lines @@
           type_info.to_native_info(argument, self._interface.id)
 
       def AllowsNull():
         assert argument.ext_attrs.get('TreatNullAs', 'NullString') == 'NullString'
         if argument.ext_attrs.get('TreatNullAs') == 'NullString':
           return True
 
         if argument.type.nullable:
           return True
 
+        if isinstance(argument, IDLAttribute):
+          return (argument.type.id == 'DOMString') and \
+              ('Reflect' in argument.ext_attrs)
+
         if isinstance(argument, IDLArgument):
           if IsOptional(argument) and not self._IsArgumentOptionalInWebCore(node, argument):
             return True
           if argument.ext_attrs.get('Default') == 'NullString':
             return True
           if _IsOptionalStringArgumentInInitEventMethod(self._interface, node, argument):
             return True
 
         return False
 
@@ skipping 210 matching lines @@
             '    if (Dart_NativeFunction func = $CLASS_NAME::resolver(name, argumentCount))\n'
             '        return func;\n',
             CLASS_NAME=os.path.splitext(os.path.basename(path))[0])
 
 def _IsOptionalStringArgumentInInitEventMethod(interface, operation, argument):
   return (
       interface.id.endswith('Event') and
       operation.id.startswith('init') and
       argument.ext_attrs.get('Default') == 'Undefined' and
       argument.type.id == 'DOMString')