Implement fullNameForErrors on all Builders.

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;
 
 import '../messages.dart' show nit;
 
@@ skipping 150 matching lines @@
   bool get isConstructor => false;
 
   bool get isFactory => false;
 
   bool get isLocal => false;
 
   get target => internalError("Unsupported operation $runtimeType.");
 
   bool get hasProblem => false;
 
+  String get fullNameForErrors;
+
   static Uri getUri(Builder builder) {
     if (builder == null) return internalError("Builder is null.");
     while (builder != null) {
       if (builder is LibraryBuilder) return builder.uri;
       builder = builder.parent;
     }
     return internalError("No library parent.");
   }
 }