Include characterHex in all encoding errors.

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

 // Copyright (c) 2012, 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.parser.parser;
 
 import '../scanner.dart' show
     ErrorToken;
 
 import '../scanner/recover.dart' show
@@ skipping 3268 matching lines @@
     } else {
       arguments ??= {};
       listener.handleRecoverableError(token, kind, arguments);
     }
   }
 
   Token reportErrorToken(ErrorToken token, bool isRecoverable) {
     ErrorKind kind = token.errorCode;
     Map arguments = const {};
     switch (kind) {
+      case ErrorKind.AsciiControlCharacter:
       case ErrorKind.NonAsciiIdentifier:
+      case ErrorKind.NonAsciiWhitespace:
+      case ErrorKind.Encoding:
         String hex = token.character.toRadixString(16);
         if (hex.length < 4) {
           String padding = "0000".substring(hex.length);
           hex = "$padding$hex";
         }
         arguments = {'characterHex': hex};
         break;
 
       case ErrorKind.UnterminatedString:
         arguments = {'quote': token.start};
@@ skipping 13 matching lines @@
         break;
     }
     if (isRecoverable) {
       listener.handleRecoverableError(token, kind, arguments);
       return null;
     } else {
       return listener.handleUnrecoverableError(token, kind, arguments);
     }
   }
 }