Explicitly implementing some DOM iterable APIs for performance

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
@@ skipping 410 matching lines @@
     # and
     #
     #   class YImpl extends ListBase<T> { copies of transitive XImpl methods; }
     #
     dart_element_type = self._DartType(element_type)
     if self._HasNativeIndexGetter():
       self._EmitNativeIndexGetter(dart_element_type)
     else:
       self._members_emitter.Emit(
           '\n'
-          '  $TYPE operator[](int index) native "$(INTERFACE)_item_Callback";\n',
+          '  $TYPE operator[](int index) {\n'
+          '    if (index < 0 || index >= length)\n'
+          '      throw new RangeError.range(index, 0, length);\n'
+          '    return _nativeIndexedGetter(index);\n'
+          '  }\n'
+          '  $TYPE _nativeIndexedGetter(int index) native "$(INTERFACE)_item_Callback";\n',
           TYPE=self.SecureOutputType(element_type),
           INTERFACE=self._interface.id)
 
     if self._HasNativeIndexSetter():
       self._EmitNativeIndexSetter(dart_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'
@@ skipping 505 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')