Remove Fasta's copy of accessors.dart.

pkg/front_end/lib/src/fasta/names.dart

 // Copyright (c) 2017, 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 front_end.src.fasta.names;
 
 import 'package:kernel/ast.dart' show Name;
 
+export 'package:kernel/frontend/accessors.dart' show indexGetName, indexSetName;
+
 final Name callName = new Name("call");
 
 final Name plusName = new Name("+");
 
 final Name minusName = new Name("-");
 
 final Name multiplyName = new Name("*");
 
 final Name divisionName = new Name("/");
 
 final Name percentName = new Name("%");
 
 final Name ampersandName = new Name("&");
 
 final Name leftShiftName = new Name("<<");
 
 final Name rightShiftName = new Name(">>");
 
 final Name caretName = new Name("^");
 
 final Name barName = new Name("|");
 
 final Name mustacheName = new Name("~/");
-
-final Name indexGetName = new Name("[]");
-
-final Name indexSetName = new Name("[]=");