Fix crash when reporting error involving constructor.

pkg/front_end/lib/src/fasta/kernel/body_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.body_builder;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
 
 import '../parser/error_kind.dart' show ErrorKind;
 
@@ skipping 2685 matching lines @@
 
 String getNodeName(Object node) {
   if (node is Identifier) {
     return node.name;
   } else if (node is UnresolvedIdentifier) {
     return node.name.name;
   } else if (node is TypeDeclarationBuilder) {
     return node.name;
   } else if (node is PrefixBuilder) {
     return node.name;
-  } else if (node is ThisPropertyAccessor) {
-    return node.name.name;
+  } else if (node is ThisAccessor) {
+    return node.isSuper ? "super" : "this";
+  } else if (node is BuilderAccessor) {
+    return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }