merge PrecedenceInfo into TokenType and update all refs

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

 // Copyright (c) 2017, 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 licenset hat can be found in the LICENSE file.
 
 library dart_scanner.error_token;
 
 import '../../scanner/token.dart' show TokenType;
 
 import '../fasta_codes.dart'
     show
         FastaCode,
         codeAsciiControlCharacter,
         codeEncoding,
         codeExpectedHexDigit,
         codeMissingExponent,
         codeNonAsciiIdentifier,
         codeNonAsciiWhitespace,
         codeUnexpectedDollarInString,
         codeUnmatchedToken,
         codeUnterminatedComment,
         codeUnterminatedString,
         codeUnterminatedToken;
 
 import '../scanner.dart'
     show BeginGroupToken, Token, unicodeReplacementCharacter;
 
-import 'precedence.dart' show BAD_INPUT_INFO;
-
 ErrorToken buildUnexpectedCharacterToken(int character, int charOffset) {
   if (character < 0x1f) {
     return new AsciiControlCharacterToken(character, charOffset);
   }
   switch (character) {
     case unicodeReplacementCharacter:
       return new EncodingErrorToken(charOffset);
 
     /// See [General Punctuation]
     /// (http://www.unicode.org/charts/PDF/U2000.pdf).
@@ skipping 25 matching lines @@
   }
 }
 
 /// Common superclass for all error tokens.
 ///
 /// It's considered an implementation error to access [lexeme] of an
 /// [ErrorToken].
 abstract class ErrorToken extends Token {
   ErrorToken(int charOffset) : super(charOffset);
 
-  TokenType get info => BAD_INPUT_INFO;
+  TokenType get info => TokenType.BAD_INPUT;
 
   String get lexeme => throw assertionMessage;
 
   String get stringValue => null;
 
   bool isIdentifier() => false;
 
   String get assertionMessage;
 
   FastaCode get errorCode;
@@ skipping 134 matching lines @@
   UnmatchedToken(BeginGroupToken begin)
       : this.begin = begin,
         super(begin.charOffset);
 
   String toString() => "UnmatchedToken(${begin.lexeme})";
 
   String get assertionMessage => "'$begin' isn't closed.";
 
   FastaCode get errorCode => codeUnmatchedToken;
 }