Use `Function` as function type syntax.

pkg/compiler/lib/src/library_loader.dart

Index: pkg/compiler/lib/src/library_loader.dart
diff --git a/pkg/compiler/lib/src/library_loader.dart b/pkg/compiler/lib/src/library_loader.dart
index c7c6e86a39067e77bf3ee672be77a370b4f4b2f2..e0b316b524ed16f0a78f83cb6c5c2ab3fd834d38 100644
--- a/pkg/compiler/lib/src/library_loader.dart
+++ b/pkg/compiler/lib/src/library_loader.dart
@@ -34,9 +34,6 @@ 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.
  *
@@ -170,7 +167,9 @@ abstract class LibraryLoaderTask implements LibraryProvider, CompilerTask {
 
   /// 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