dart2js_html: Fix for issue 29538 - some returned lists may be null

tools/dom/scripts/dartmetadata.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 to provide Dart metadata for
 DOM APIs.
 """
 
 import copy
@@ skipping 74 matching lines @@
     'Document.getElementsByName': [
       "@Creates('NodeList|HtmlCollection')",
       "@Returns('NodeList|HtmlCollection')",
     ],
 
     'Document.getElementsByTagName': [
       "@Creates('NodeList|HtmlCollection')",
       "@Returns('NodeList|HtmlCollection')",
     ],
 
+    # querysSelectorAll never returns `null`.
+    'Document.querySelectorAll': [
+      "@Creates('NodeList')",
+      "@Returns('NodeList')",
+    ],
+    'DocumentFragment.querySelectorAll': [
+      "@Creates('NodeList')",
+      "@Returns('NodeList')",
+    ],
+    'Element.querySelectorAll': [
+      "@Creates('NodeList')",
+      "@Returns('NodeList')",
+    ],
+
     # Methods returning Window can return a local window, or a cross-frame
     # window (=Object) that needs wrapping.
     'Window': [
       "@Creates('Window|=Object')",
       "@Returns('Window|=Object')",
     ],
 
     'Window.openDatabase': [
       "@Creates('SqlDatabase')",
     ],
@@ skipping 787 matching lines @@
       pass
     else:
       _logger.warn('Unknown support_level - %s:%s' % (interface_id, member_id))
 
     return annotations
 
   def Flush(self):
     json_file = open(self._api_status_path, 'w+')
     json.dump(self._types, json_file, indent=2, separators=(',', ': '), sort_keys=True)
     json_file.close()