Do not add secondary interfaces implemented by parents.

lib/html/scripts/systemhtml.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
 import os
@@ skipping 536 matching lines @@
         TYPE=events_class)
 
   def _TransitiveSecondaryParents(self, interface):
     """Returns a list of all non-primary parents.
 
     The list contains the interface objects for interfaces defined in the
     database, and the name for undefined interfaces.
     """
     def walk(parents):
       for parent in parents:
-        if IsDartCollectionType(parent.type.id):
-          result.append(parent.type.id)
+        parent_name = parent.type.id
+        if parent_name == 'EventTarget':
+          # Currently EventTarget is implemented as a mixin, not a proper
+          # super interface---ignore its members.
           continue
-        if self._database.HasInterface(parent.type.id):
-          parent_interface = self._database.GetInterface(parent.type.id)
+        if IsDartCollectionType(parent_name):
+          result.append(parent_name)
+          continue
+        if self._database.HasInterface(parent_name):
+          parent_interface = self._database.GetInterface(parent_name)
           result.append(parent_interface)
           walk(parent_interface.parents)
 
     result = []
     if interface.parents:
       parent = interface.parents[0]
       if IsPureInterface(parent.type.id):
         walk(interface.parents)
       else:
         walk(interface.parents[1:])
@@ skipping 544 matching lines @@
 
     library_emitter = self._multiemitter.FileEmitter(library_file_path)
     library_file_dir = os.path.dirname(library_file_path)
     auxiliary_dir = os.path.relpath(auxiliary_dir, library_file_dir)
     imports_emitter = library_emitter.Emit(
         self._template, AUXILIARY_DIR=massage_path(auxiliary_dir))
     for path in sorted(self._path_to_emitter.keys()):
       relpath = os.path.relpath(path, library_file_dir)
       imports_emitter.Emit(
           "part '$PATH';\n", PATH=massage_path(relpath))