Implement type variables in mixin applications.

pkg/front_end/lib/src/fasta/builder/class_builder.dart

 // Copyright (c) 2016, 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 fasta.class_builder;
 
 import 'builder.dart' show
     Builder,
     ConstructorReferenceBuilder,
     LibraryBuilder,
@@ skipping 15 matching lines @@
   List<T> interfaces;
 
   final Map<String, Builder> members;
 
   ClassBuilder(
       List<MetadataBuilder> metadata, int modifiers,
       String name, this.typeVariables, this.supertype, this.interfaces,
       this.members, LibraryBuilder parent, int charOffset)
       : super(metadata, modifiers, name, parent, charOffset);
 
+  /// Returns true if this class is the result of applying a mixin to its
+  /// superclass.
+  bool get isMixinApplication => mixedInType != null;
+
+  T get mixedInType;
+
   List<ConstructorReferenceBuilder> get constructorReferences => null;
 
   Map<String, Builder> get constructors;
 
   Map<String, Builder> get membersInScope => members;
 
   int resolveConstructors(LibraryBuilder library) {
     if (constructorReferences == null) return 0;
     Scope scope = computeInstanceScope(library.scope);
     for (ConstructorReferenceBuilder ref in constructorReferences) {
@@ skipping 37 matching lines @@
       return null;
     } else if (isSetter && builder.isGetter) {
       return null;
     } else {
       return builder.isInstanceMember ? null : builder;
     }
   }
 
   Builder findConstructorOrFactory(String name);
 }