Ensure locations are always provided, but don't store them yet.

pkg/front_end/lib/src/fasta/builder/named_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.named_mixin_application_builder;
 
 import 'builder.dart' show
     Builder,
     ClassBuilder,
     LibraryBuilder,
     MetadataBuilder,
     TypeBuilder,
     TypeVariableBuilder;
 
 abstract class NamedMixinApplicationBuilder<T extends TypeBuilder, R>
     extends ClassBuilder<T, R> {
   NamedMixinApplicationBuilder(
       List<MetadataBuilder> metadata, String name,
       List<TypeVariableBuilder> typeVariables, int modifiers, T supertype,
-      List<T> interfaces, List<T> types, LibraryBuilder parent)
+      List<T> interfaces, List<T> types, LibraryBuilder parent, int charOffset)
       : super(metadata, modifiers, name, typeVariables, supertype, interfaces,
-          <String, Builder>{}, types, parent);
+          <String, Builder>{}, types, parent, charOffset);
 
   T get mixinApplication => supertype;
 }