Deferred (aka lazy) loading of static functions.

dart/sdk/lib/core/load_async.dart

 // 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.
 
 /**
  * Indicates that loading of [libraryName] is deferred.
  *
  * Applies to library imports.
  *
  * Example usage:
@@ skipping 23 matching lines @@
  * Indicates that an element is not called until [libraryName] has
  * been loaded.
  *
  * Applies to library declarations, classes, and functions.
  */
 class OnLibraryLoaded {
   final String libraryName;
 
   const OnLibraryLoaded(this.libraryName);
 }
-
-/**
- * Ensure that [libraryName] has been loaded.
- *
- * The returned future if this invocation of [load] caused the library
- * to be loaded.
- */
-external Future<bool> load(String libraryName, {String uri});