Use `Function` as function type syntax.

pkg/compiler/lib/src/library_loader.dart

 // 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.
 
 library dart2js.library_loader;
 
 import 'dart:async';
 
 import 'common/names.dart' show Uris;
 import 'common/tasks.dart' show CompilerTask, Measurer;
@@ skipping 16 matching lines @@
         LibraryDependencyElementX,
         PrefixElementX,
         SyntheticImportElement;
 import 'environment.dart';
 import 'resolved_uri_translator.dart';
 import 'script.dart';
 import 'serialization/serialization.dart' show LibraryDeserializer;
 import 'tree/tree.dart';
 import 'util/util.dart' show Link, LinkBuilder;
 
-typedef Future<Iterable<LibraryElement>> ReuseLibrariesFunction(
-    Iterable<LibraryElement> libraries);
-
 /**
  * [CompilerTask] for loading libraries and setting up the import/export scopes.
  *
  * The library loader uses four different kinds of URIs in different parts of
  * the loading process.
  *
  * ## User URI ##
  *
  * A 'user URI' is a URI provided by the user in code and as the main entry URI
  * at the command line. These generally come in 3 versions:
@@ skipping 113 matching lines @@
   /// libraries matching [reuseLibrary] are reused.
   ///
   /// This method is used for incremental compilation.
   void reset({bool reuseLibrary(LibraryElement library)});
 
   /// Asynchronous version of [reset].
   Future resetAsync(Future<bool> reuseLibrary(LibraryElement library));
 
   /// Similar to [resetAsync] but [reuseLibrary] maps all libraries to a list
   /// of libraries that can be reused.
-  Future<Null> resetLibraries(ReuseLibrariesFunction reuseLibraries);
+  Future<Null> resetLibraries(
+      Future<Iterable<LibraryElement>> Function(Iterable<LibraryElement>)
+        reuseLibraries);
 }
 
 /// Interface for an entity that provide libraries. For instance from normal
 /// library loading or from deserialization.
 // TODO(johnniwinther): Use this to integrate deserialized libraries better.
 abstract class LibraryProvider {
   /// Looks up the library with the [canonicalUri].
   LibraryElement lookupLibrary(Uri canonicalUri);
 }
 
@@ skipping 1333 matching lines @@
   Future onLibrariesLoaded(LoadedLibraries results);
 
   /// Called whenever a library element is created.
   void onLibraryCreated(LibraryElement library);
 
   /// Called whenever a library is scanned from a script file.
   Future onLibraryScanned(LibraryElement library, LibraryLoader loader);
 }
 
 const _reuseLibrarySubtaskName = "Reuse library";