Rewrite mixin application handling in Fasta.

pkg/front_end/lib/src/fasta/builder/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.builder;
 
 import '../errors.dart' show internalError;
 
 export 'class_builder.dart' show ClassBuilder;
 
 export 'field_builder.dart' show FieldBuilder;
 
 export 'library_builder.dart' show LibraryBuilder;
 
 export 'procedure_builder.dart' show ProcedureBuilder;
 
 export 'type_builder.dart' show TypeBuilder;
 
 export 'formal_parameter_builder.dart' show FormalParameterBuilder;
 
 export 'metadata_builder.dart' show MetadataBuilder;
 
 export 'type_variable_builder.dart' show TypeVariableBuilder;
 
 export 'function_type_alias_builder.dart' show FunctionTypeAliasBuilder;
 
-export 'named_mixin_application_builder.dart' show NamedMixinApplicationBuilder;
-
 export 'mixin_application_builder.dart' show MixinApplicationBuilder;
 
 export 'enum_builder.dart' show EnumBuilder;
 
 export 'type_declaration_builder.dart' show TypeDeclarationBuilder;
 
 export 'named_type_builder.dart' show NamedTypeBuilder;
 
 export 'constructor_reference_builder.dart' show ConstructorReferenceBuilder;
 
@@ skipping 89 matching lines @@
 
   Uri computeLibraryUri() {
     Builder builder = this;
     do {
       if (builder is LibraryBuilder) return builder.uri;
       builder = builder.parent;
     } while (builder != null);
     return internalError("No library parent.");
   }
 }