Refactor Future constructors.

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

 // Copyright (c) 2013, 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 $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   @DomName('IDBCursor.delete')
   Future delete() {
    try {
       return _completeRequest($dom_delete());
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
   @DomName('IDBCursor.value')
   Future update(value) {
    try {
       return _completeRequest($dom_update(value));
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
   $!MEMBERS
 }