Implement type variables in mixin applications.

pkg/front_end/lib/src/fasta/builder/mixin_application_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.mixin_application_builder;
 
 import '../errors.dart' show
     internalError;
 
 import 'builder.dart' show
     TypeBuilder,
-    TypeDeclarationBuilder;
+    TypeDeclarationBuilder,
+    TypeVariableBuilder;
 
 import 'scope.dart' show
     Scope;
 
 abstract class MixinApplicationBuilder<T extends TypeBuilder>
     extends TypeBuilder {
   final T supertype;
   final List<T> mixins;
 
   MixinApplicationBuilder(this.supertype, this.mixins, int charOffset,
       Uri fileUri)
       : super(charOffset, fileUri);
 
+  void set typeVariables(List<TypeVariableBuilder> variables);
+
+  /// If this mixin application uses type variables, it needs a unique name
+  /// based on its subclass. If this name is provided, the name will be
+  /// `name^mixin`, otherwise it'll be `superclass&mixin`.
+  //
+  // TODO(ahe): This is to reduce diff against dartk. Consider if this is
+  // necessary.
+  void set subclassName(String value);
+
   String get name => null;
 
   void resolveIn(Scope scope) {
     supertype.resolveIn(scope);
     for (T t in mixins) {
       t.resolveIn(scope);
     }
   }
 
   void bind(TypeDeclarationBuilder builder) {
     internalError("Internal error: can't bind a mixin application.");
   }
 
   String get debugName => "MixinApplicationBuilder";
 
   StringBuffer printOn(StringBuffer buffer) {
     buffer.write(supertype);
     buffer.write(" with ");
     bool first = true;
     for (T t in mixins) {
       if (!first) buffer.write(", ");
       first = false;
       t.printOn(buffer);
     }
     return buffer;
   }
 }