record that Gamepad.buttons creates GamepadButtons

tools/dom/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 logging
@@ skipping 820 matching lines @@
   def HasIndexedGetter(self):
     ext_attrs = self._interface.ext_attrs
     has_indexed_getter = 'CustomIndexedGetter' in ext_attrs
     for operation in self._interface.operations:
       if operation.id == 'item' and 'getter' in operation.specials \
           and not self._OperationRequiresConversions(operation):
         has_indexed_getter = True
         break
     return has_indexed_getter
 
-  def AddIndexer(self, element_type):
+  def AddIndexer(self, element_type, nullable):
     """Adds all the methods required to complete implementation of List."""
     # We would like to simply inherit the implementation of everything except
     # length, [], and maybe []=.  It is possible to extend from a base
     # array implementation class only when there is no other implementation
     # inheritance.  There might be no implementation inheritance other than
     # DOMBaseWrapper for many classes, but there might be some where the
     # array-ness is introduced by a non-root interface:
     #
     #   interface Y extends X, List<T> ...
     #
     # In the non-root case we have to choose between:
     #
     #   class YImpl extends XImpl { add List<T> methods; }
     #
     # and
     #
     #   class YImpl extends ListBase<T> { copies of transitive XImpl methods; }
     #
 
     has_indexed_getter = self.HasIndexedGetter()
 
     if has_indexed_getter:
-      indexed_getter = ('JS("%s", "#[#]", this, index)' %
-          self.SecureOutputType(element_type));
+      indexed_getter = ('JS("%s%s", "#[#]", this, index)' %
+          (self.SecureOutputType(element_type), "|Null" if nullable else ""));
     elif any(op.id == 'getItem' for op in self._interface.operations):
       indexed_getter = 'this.getItem(index)'
     elif any(op.id == 'item' for op in self._interface.operations):
       indexed_getter = 'this.item(index)'
 
     if indexed_getter:
       self._members_emitter.Emit(
           '\n'
           '  $TYPE operator[](int index) {\n'
           '    if (JS("bool", "# >>> 0 !== # || # >= #", index,\n'
@@ skipping 11 matching lines @@
           ' JS("void", "#[#] = #", this, index, value); }',
           TYPE=self._NarrowInputType(element_type))
     else:
       self._members_emitter.Emit(
           '\n'
           '  void operator[]=(int index, $TYPE value) {\n'
           '    throw new UnsupportedError("Cannot assign element of immutable List.");\n'
           '  }\n',
           TYPE=self._NarrowInputType(element_type))
 
-    self.EmitListMixin(self._DartType(element_type))
+    self.EmitListMixin(self._DartType(element_type), nullable)
 
   def EmitAttribute(self, attribute, html_name, read_only):
     if self._HasCustomImplementation(attribute.id):
       return
 
     if IsPureInterface(self._interface.id, self._database):
       self._AddInterfaceAttribute(attribute, html_name, read_only)
       return
 
     # If the attribute is shadowing, we can't generate a shadowing
@@ skipping 436 matching lines @@
 
   def AddFile(self, basename, library_name, path):
     self._libraries[library_name].AddFile(path)
 
   def AddTypeEntry(self, library_name, idl_name, dart_name):
     self._libraries[library_name].AddTypeEntry(idl_name, dart_name)
 
   def Emit(self, emitter, auxiliary_dir):
     for lib in self._libraries.values():
       lib.Emit(emitter, auxiliary_dir)