Use non-pinned IDL for Dartium code gen

lib/dom/scripts/fremontcutbuilder.py

 #!/usr/bin/python
 # Copyright (c) 2011, 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.
 
 import database
 import databasebuilder
 import idlparser
 import os.path
 import logging.config
@@ skipping 131 matching lines @@
         'Exception': 'DOMException',     # NotificationCenter.createNotification
         'SharedWorkerContext': 'SharedWorkerGlobalScope',
         'WorkerContext': 'WorkerGlobalScope',
       })
 
   optional_argument_whitelist = [
       ('CSSStyleDeclaration', 'setProperty', 'priority'),
       ('IDBDatabase', 'transaction', 'mode'),
       ]
 
-  # Assume standard Dart checkout.
-  webcore_path = os.path.join(current_dir, '..', '..', '..',
-                              'third_party', 'WebCore')
+  # Assume Dartium checkout.
+  webcore_path = os.path.join(current_dir, '..', '..', '..', '..',
+                              'third_party', 'WebKit', 'Source', 'WebCore')
 
   if not os.path.exists(webcore_path):
-    # Dartium checkout.
-    webcore_path = os.path.join(current_dir, '..', '..', '..', '..',
-                                'third_party', 'WebKit', 'Source', 'WebCore')
+    # Fall back to standard Dart checkout.
+    webcore_path = os.path.join(current_dir, '..', '..', '..',
+                                'third_party', 'WebCore')
 
   for dir_name in webkit_dirs:
     dir_path = os.path.join(webcore_path, dir_name)
     builder.import_idl_directory(dir_path, webkit_options)
 
   webkit_supplemental_options = databasebuilder.DatabaseBuilderOptions(
     idl_syntax=idlparser.FREMONTCUT_SYNTAX,
     source='WebKit',
     rename_operation_arguments_on_merge=True)
   builder.import_idl_file(
@@ skipping 20 matching lines @@
 
   builder.fix_displacements('WebKit')
 
   # Cleanup:
   builder.normalize_annotations(['WebKit', 'Dart'])
 
   db.Save()
 
 if __name__ == '__main__':
   sys.exit(main())