cleanup fasta token classes

pkg/front_end/lib/src/fasta/kernel/body_builder.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.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, MemberKind, optional;
@@ skipping 18 matching lines @@
 import 'package:kernel/clone.dart' show CloneVisitor;
 
 import 'package:kernel/transformations/flags.dart' show TransformerFlag;
 
 import 'package:kernel/class_hierarchy.dart' show ClassHierarchy;
 
 import 'package:kernel/core_types.dart' show CoreTypes;
 
 import 'frontend_accessors.dart' show buildIsNull, makeBinary, makeLet;
 
-import '../../scanner/token.dart' show Token;
+import '../../scanner/token.dart' show BeginToken, Token;
 
-import '../scanner/token.dart'
-    show BeginGroupToken, isBinaryOperator, isMinusOperator;
+import '../scanner/token.dart' show isBinaryOperator, isMinusOperator;
 
 import '../errors.dart' show InputError, formatUnexpected, internalError;
 
 import '../source/scope_listener.dart'
     show JumpTargetKind, NullValue, ScopeListener;
 
 import '../scope.dart' show ProblemBuilder;
 
 import 'fasta_accessors.dart';
 
@@ skipping 524 matching lines @@
           arguments.getRange(0, firstNamedArgumentIndex));
       List<NamedExpression> named = new List<NamedExpression>.from(
           arguments.getRange(firstNamedArgumentIndex, arguments.length));
       push(new KernelArguments(positional, named: named));
     } else {
       push(new KernelArguments(arguments));
     }
   }
 
   @override
-  void handleParenthesizedExpression(BeginGroupToken token) {
+  void handleParenthesizedExpression(BeginToken token) {
     debugEvent("ParenthesizedExpression");
     push(new ParenthesizedExpression(this, popForValue(), token.endGroup));
   }
 
   @override
   void endSend(Token beginToken, Token endToken) {
     debugEvent("Send");
     Arguments arguments = pop();
     List<DartType> typeArguments = pop();
     Object receiver = pop();
@@ skipping 2600 matching lines @@
     if (starToken == null) {
       return AsyncMarker.Async;
     } else {
       assert(identical(starToken.stringValue, "*"));
       return AsyncMarker.AsyncStar;
     }
   } else {
     return internalError("Unknown async modifier: $asyncToken");
   }
 }