fix scriptTag scanner_round_trip test

pkg/analyzer/lib/src/fasta/token_utils.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.analyzer.token_utils;
 
 import 'package:front_end/src/fasta/parser/error_kind.dart' show ErrorKind;
 
 import 'package:front_end/src/fasta/scanner/error_token.dart' show ErrorToken;
 
@@ skipping 333 matching lines @@
     case TokenType.KEYWORD:
       var keyword = Keyword.keywords[token.lexeme];
       if (keyword != null) {
         return new KeywordToken(keyword, token.offset);
       } else {
         return internalError("Unrecognized keyword: '${token.lexeme}'.");
       }
       break;
     case TokenType.MULTI_LINE_COMMENT:
       return string(MULTI_LINE_COMMENT_INFO);
-    // case TokenType.SCRIPT_TAG
+    case TokenType.SCRIPT_TAG:
+      return string(SCRIPT_INFO);
     case TokenType.SINGLE_LINE_COMMENT:
       return string(SINGLE_LINE_COMMENT_INFO);
     case TokenType.STRING:
       return string(STRING_INFO);
     case TokenType.AMPERSAND:
       return symbol(AMPERSAND_INFO);
     case TokenType.AMPERSAND_AMPERSAND:
       return symbol(AMPERSAND_AMPERSAND_INFO);
     // case TokenType.AMPERSAND_AMPERSAND_EQ
     case TokenType.AMPERSAND_EQ:
@@ skipping 417 matching lines @@
     case PERIOD_PERIOD_PERIOD_TOKEN:
       return TokenType.PERIOD_PERIOD_PERIOD;
     // case GENERIC_METHOD_TYPE_LIST_TOKEN:
     //   return TokenType.GENERIC_METHOD_TYPE_LIST;
     // case GENERIC_METHOD_TYPE_ASSIGN_TOKEN:
     //   return TokenType.GENERIC_METHOD_TYPE_ASSIGN;
     default:
       return internalError("Unhandled token ${token.info}");
   }
 }