Add "contains" method to Collection.

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 323 matching lines @@
         self._interface, self._database)
     if element_type:
       self._members_emitter.Emit(
           '\n'
           '  factory $CTOR(int length) =>\n'
           '    $FACTORY.create$(CTOR)(length);\n'
           '\n'
           '  factory $CTOR.fromList(List<$TYPE> list) =>\n'
           '    $FACTORY.create$(CTOR)_fromList(list);\n'
           '\n'
-          '  factory $CTOR.fromBuffer(ArrayBuffer buffer, [int byteOffset, int length]) => \n'
+          '  factory $CTOR.fromBuffer(ArrayBuffer buffer, [int byteOffset, int length]) =>\n'
           '    $FACTORY.create$(CTOR)_fromBuffer(buffer, byteOffset, length);\n',
         CTOR=self._interface.id,
         TYPE=self._DartType(element_type),
         FACTORY=factory_provider)
 
     events_interface = self._event_generator.ProcessInterface(
         self._interface, self._html_interface_name,
         self._backend.CustomJSMembers(),
         interface_emitter, implementation_emitter)
     if events_interface:
@@ skipping 769 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(
           "#source('$PATH');\n", PATH=massage_path(relpath))