Fixing up DOM constructors.

tools/dom/scripts/htmldartgenerator.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."""
 
 import emitter
 from generator import AnalyzeOperation, ConstantOutputOrder, \
@@ skipping 473 matching lines @@
             (',\n        %s(error) { completer.completeError(error); }' %
             ('%s : ' % info.callback_args[1].name
             if info.requires_named_arguments and
                 info.callback_args[1].is_optional else ''))),
         FUTURE_GENERIC = ('' if len(callback_info.param_infos) == 0 or
             not callback_info.param_infos[0].type_id else
             '<%s>' % self._DartType(callback_info.param_infos[0].type_id)),
         ORIGINAL_FUNCTION = html_name)
 
   def EmitHelpers(self, base_class):
-    pass
+    if not self._members_emitter:
+      return
+
+    if base_class != self.RootClassName():
+      self._members_emitter.Emit(
+          '  // To suppress missing implicit constructor warnings.\n'
+          '  factory $CLASSNAME._() { '
+          'throw new UnsupportedError("Not supported"); }\n',
+          CLASSNAME=self._interface_type_info.implementation_name())
 
   def DeclareAttribute(self, attribute, type_name, attr_name, read_only):
     """ Declares an attribute but does not include the code to invoke it.
     """
     if read_only:
       template = '\n  $TYPE get $NAME;\n'
     else:
       template = '\n  $TYPE $NAME;\n'
 
     self._members_emitter.Emit(template,
@@ skipping 80 matching lines @@
     if interface.parents:
       parent = interface.parents[0]
       if IsPureInterface(parent.type.id):
         walk(interface.parents)
       else:
         walk(interface.parents[1:])
     return result
 
   def _DartType(self, type_name):
     return self._type_registry.DartType(type_name)