Adding supported checks and flags to window.performance.

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 os
@@ skipping 67 matching lines @@
   'HTMLKeygenElement': "Element.isTagSupported('keygen') "
       "&& (new Element.tag('keygen') is KeygenElement)",
   'HTMLMarqueeElement': "Element.isTagSupported('marquee')"
       "&& (new Element.tag('marquee') is MarqueeElement)",
   'HTMLMeterElement': "Element.isTagSupported('meter')",
   'HTMLObjectElement': "Element.isTagSupported('object')",
   'HTMLOutputElement': "Element.isTagSupported('output')",
   'HTMLProgressElement': "Element.isTagSupported('progress')",
   'HTMLShadowElement': "Element.isTagSupported('shadow')",
   'HTMLTrackElement': "Element.isTagSupported('track')",
+  'Performance': "JS('bool', '!!(window.performance)')",
   'WebSocket': "JS('bool', 'typeof window.WebSocket != \"undefined\"')",
 }
 
 # Classes that offer only static methods, and therefore we should suppress
 # constructor creation.
 _static_classes = set(['Url'])
 
 # Information for generating element constructors.
 #
 # TODO(sra): maybe remove all the argument complexity and use cascades.
@@ skipping 937 matching lines @@
     for library_name in libraries:
       self._libraries[library_name] = DartLibrary(
           library_name, template_loader, library_type, output_dir)
 
   def AddFile(self, basename, library_name, path):
     self._libraries[library_name].AddFile(path)
 
   def Emit(self, emitter, auxiliary_dir):
     for lib in self._libraries.values():
       lib.Emit(emitter, auxiliary_dir)