Refactor Future constructors.

tools/dom/templates/html/impl/impl_IDBIndex.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('IDBIndex.count')
   Future<int> count([key_OR_range]) {
    try {
       var request;
       if (key_OR_range != null) {
         request = $dom_count(key_OR_range);
       } else {
         request = $dom_count();
       }
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
   @DomName('IDBIndex.get')
   Future get(key) {
     try {
       var request = $dom_get(key);
 
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
   @DomName('IDBIndex.getKey')
   Future getKey(key) {
     try {
       var request = $dom_getKey(key);
 
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
   /**
    * Creates a stream of cursors over the records in this object store.
    *
    * See also:
    *
    * * [ObjectStore.openCursor]
    */
@@ skipping 39 matching lines @@
     if (direction == null) {
       request = $dom_openKeyCursor(key_OR_range);
     } else {
       request = $dom_openKeyCursor(key_OR_range, direction);
     }
     return ObjectStore._cursorStreamFromResult(request, autoAdvance);
   }
 
   $!MEMBERS
 }