Adding supported checks to websql.

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 54 matching lines @@
     'Window.location',
     'Window.open',
     'Window.requestAnimationFrame',
     'Window.webkitCancelAnimationFrame',
     'Window.webkitRequestAnimationFrame',
     'WorkerContext.indexedDB',
     ])
 
 js_support_checks = {
   'ArrayBuffer': "JS('bool', 'typeof window.ArrayBuffer != \"undefined\"')",
+  'Database': "JS('bool', '!!(window.openDatabase)')",
   'DOMApplicationCache': "JS('bool', '!!(window.applicationCache)')",
   'DOMFileSystem': "JS('bool', '!!(window.webkitRequestFileSystem)')",
   'HashChangeEvent': "Event._isTypeSupported('HashChangeEvent')",
   'HTMLContentElement': "Element.isTagSupported('content')",
   'HTMLDataListElement': "Element.isTagSupported('datalist')",
   'HTMLDetailsElement': "Element.isTagSupported('details')",
   'HTMLEmbedElement': "Element.isTagSupported('embed')",
   # IE creates keygen as Block elements
   'HTMLKeygenElement': "Element.isTagSupported('keygen') "
       "&& (new Element.tag('keygen') is KeygenElement)",
@@ skipping 953 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)