Introduce TypedefEntity

pkg/compiler/lib/src/js_emitter/sorter.dart

 // Copyright (c) 2017, 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.js_emitter.sorter;
 
 import '../elements/elements.dart';
 import '../elements/entities.dart';
 
 /// Sorting strategy for libraries, classes and members.
 abstract class Sorter {
   /// Returns a sorted list of [libraries].
   Iterable<LibraryEntity> sortLibraries(Iterable<LibraryEntity> libraries);
 
   /// Returns a sorted list of [classes].
   Iterable<ClassEntity> sortClasses(Iterable<ClassEntity> classes);
 
+  /// Returns a sorted list of [typedefs].
+  Iterable<TypedefEntity> sortTypedefs(Iterable<TypedefEntity> typedefs);
+
   /// Returns a sorted list of [members].
   Iterable<MemberEntity> sortMembers(Iterable<MemberEntity> members);
 }
 
 class ElementSorter implements Sorter {
   const ElementSorter();
 
   @override
   List<LibraryEntity> sortLibraries(Iterable<LibraryEntity> libraries) {
     return Elements.sortedByPosition(new List.from(libraries, growable: false));
   }
 
   @override
   List<ClassEntity> sortClasses(Iterable<ClassEntity> classes) {
     return Elements.sortedByPosition(new List.from(classes, growable: false));
   }
 
   @override
+  Iterable<TypedefEntity> sortTypedefs(Iterable<TypedefEntity> typedefs) {
+    return Elements.sortedByPosition(new List.from(typedefs, growable: false));
+  }
+
+  @override
   List<MemberEntity> sortMembers(Iterable<MemberEntity> members) {
     return Elements.sortedByPosition(new List.from(members, growable: false));
   }
 }