Handle forwarding constructors to unnamed mixin applications

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.
@@ skipping 14 matching lines @@
 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));
+    List<ClassElement> regularClasses = <ClassElement>[];
+    List<MixinApplicationElement> unnamedMixins = <MixinApplicationElement>[];
+    for (ClassElement cls in classes) {
+      if (cls.isUnnamedMixinApplication) {
+        unnamedMixins.add(cls);
+      } else {
+        regularClasses.add(cls);
+      }
+    }
+    List<ClassEntity> sorted = <ClassEntity>[];
+    sorted.addAll(Elements.sortedByPosition<ClassElement>(regularClasses));
+    unnamedMixins.sort((a, b) {
+      int result = a.name.compareTo(b.name);
+      if (result != 0) return result;
+      return Elements.compareByPosition(a.mixin, b.mixin);
+    });
+    sorted.addAll(unnamedMixins);
+    return sorted;
   }
 
   @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));
   }
 }