merge PrecedenceInfo into TokenType and update all refs

tests/compiler/dart2js/scanner_test.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.
 
 import "package:expect/expect.dart";
 import 'package:front_end/src/fasta/scanner.dart';
 import 'package:front_end/src/fasta/scanner/characters.dart';
-import 'package:front_end/src/fasta/scanner/precedence.dart';
+import 'package:front_end/src/scanner/token.dart' show TokenType;
 import 'dart:typed_data';
 
 Token scan(List<int> bytes) {
   List<int> zeroTerminated = new Uint8List(bytes.length + 1);
   zeroTerminated.setRange(0, bytes.length, bytes);
   zeroTerminated[bytes.length] = 0;
   return new Utf8BytesScanner(zeroTerminated).tokenize();
 }
 
 Token scanUTF8(List<int> bytes) {
@@ skipping 158 matching lines @@
     // UTF-8: F0 90 90 92
     token = scanUTF8([0xf0, 0x90, 0x90, 0x92]);
     Expect.stringEquals("'𐐒'", token.lexeme);
   } else {
     print('Skipping non-BMP character test');
   }
 
   // Regression test for issue 1761.
   // "#!"
   token = scan([0x23, 0x21]);
-  Expect.equals(token.info, SCRIPT_INFO); // Treated as a comment.
+  Expect.equals(token.info, TokenType.SCRIPT_TAG); // Treated as a comment.
 
   // Regression test for issue 1761.
   // "#! Hello, World!"
   token = scan([
     0x23,
     0x21,
     0x20,
     0x48,
     0x65,
     0x6c,
     0x6c,
     0x6f,
     0x2c,
     0x20,
     0x57,
     0x6f,
     0x72,
     0x6c,
     0x64,
     0x21
   ]);
-  Expect.equals(token.info, SCRIPT_INFO); // Treated as a comment.
+  Expect.equals(token.info, TokenType.SCRIPT_TAG); // Treated as a comment.
 }