Make html metadata follow the spec.

tools/dom/templates/html/impl/impl_IDBFactory.darttemplate

 // 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.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   /**
    * Checks to see if Indexed DB is supported on the current platform.
    */
@@ skipping 53 matching lines @@
         completer.completeError(e);
       });
       return completer.future;
     } catch (e, stacktrace) {
       return new Future.error(e, stacktrace);
     }
   }
 
   @DomName('IDBFactory.getDatabaseNames')
   @SupportedBrowser(SupportedBrowser.CHROME)
-  @Experimental
+  @Experimental()
   Future<List<String>> getDatabaseNames() {
     try {
       var request = $dom_webkitGetDatabaseNames();
 
       return _completeRequest(request);
     } catch (e, stacktrace) {
       return new Future.error(e, stacktrace);
     }
   }
 
@@ skipping 22 matching lines @@
   // TODO: make sure that completer.complete is synchronous as transactions
   // may be committed if the result is not processed immediately.
   request.onSuccess.listen((e) {
     completer.complete(request.result);
   });
   request.onError.listen((e) {
     completer.completeError(e);
   });
   return completer.future;
 }