Implement type variables in mixin applications.

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

Index: pkg/front_end/lib/src/fasta/builder/mixin_application_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/builder/mixin_application_builder.dart b/pkg/front_end/lib/src/fasta/builder/mixin_application_builder.dart
index e7b319693bbe1ea379aa35bdf6dd679f58009781..a1fe418778e06be3ec61c61e196a9558108871f3 100644
--- a/pkg/front_end/lib/src/fasta/builder/mixin_application_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/mixin_application_builder.dart
@@ -9,7 +9,8 @@ import '../errors.dart' show
 
 import 'builder.dart' show
     TypeBuilder,
-    TypeDeclarationBuilder;
+    TypeDeclarationBuilder,
+    TypeVariableBuilder;
 
 import 'scope.dart' show
     Scope;
@@ -23,6 +24,10 @@ abstract class MixinApplicationBuilder<T extends TypeBuilder>
       Uri fileUri)
       : super(charOffset, fileUri);
 
+  void set typeVariables(List<TypeVariableBuilder> variables);
+
+  void set subclassName(String value);
+
   String get name => null;
 
   void resolveIn(Scope scope) {