Include characterHex in all encoding errors.

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

Index: pkg/front_end/lib/src/fasta/parser/parser.dart
diff --git a/pkg/front_end/lib/src/fasta/parser/parser.dart b/pkg/front_end/lib/src/fasta/parser/parser.dart
index d4b87d76d7bc4b844a05504430272da6ac915811..b1f6f876f1c3f2fbd3f698702047c5827f418aed 100644
--- a/pkg/front_end/lib/src/fasta/parser/parser.dart
+++ b/pkg/front_end/lib/src/fasta/parser/parser.dart
@@ -3286,7 +3286,10 @@ class Parser {
     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);