Fix a few hints.

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

 // Copyright (c) 2011, 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.scanner.token;
 
 import 'keyword.dart' show Keyword;
 
 import 'precedence.dart' show BAD_INPUT_INFO, EOF_INFO, PrecedenceInfo;
 
@@ skipping 106 matching lines @@
     } else {
       return lexeme.length;
     }
   }
 
   /// The character offset of the end of this token within the source text.
   int get charEnd => charOffset + charCount;
 
   bool get isEof => false;
 
-  @override
   bool get isOperator => info.isOperator;
 }
 
 /**
  * A [SymbolToken] represents the symbol in its precedence info.
  * Also used for end of file with EOF_INFO.
  */
 class SymbolToken extends Token {
   final PrecedenceInfo info;
 
@@ skipping 233 matching lines @@
       identical(value, "<=") ||
       identical(value, "<") ||
       identical(value, "&") ||
       identical(value, "^") ||
       identical(value, "|");
 }
 
 bool isTernaryOperator(String value) => identical(value, "[]=");
 
 bool isMinusOperator(String value) => identical(value, "-");