flatten Keyword into TokenType

pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart

Index: pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart
diff --git a/pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart b/pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart
index 0d12ef0179673f7397b182274fc9489defb9e8d1..d20befaceab7705f8a695fc3405563c6cda32ca1 100644
--- a/pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/array_based_scanner.dart
@@ -75,7 +75,7 @@ abstract class ArrayBasedScanner extends AbstractScanner {
    * Appends a keyword token whose kind is determined by [keyword].
    */
   void appendKeywordToken(Keyword keyword) {
-    String syntax = keyword.syntax;
+    String syntax = keyword.lexeme;
     // Type parameters and arguments cannot contain 'this'.
     if (identical(syntax, 'this')) {
       discardOpenLt();