Fix parsing [a]sync[*] function body modifiers with Fasta.

pkg/front_end/lib/src/fasta/parser/parser.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.
 
 library fasta.parser.parser;
 
 import '../scanner.dart' show ErrorToken;
 
 import '../scanner/recover.dart' show closeBraceFor, skipToEof;
 
@@ skipping 1991 matching lines @@
       if (!allowAbstract) {
         reportRecoverableError(token, ErrorKind.ExpectedBody);
       }
       listener.endFunctionBody(0, null, token);
       return token;
     } else if (optional('=>', token)) {
       Token begin = token;
       token = parseExpression(token.next);
       if (!isExpression) {
         expectSemicolon(token);
-        listener.endReturnStatement(true, begin, token);
+        listener.endExpressionFunctionBody(begin, token);
       } else {
-        listener.endReturnStatement(true, begin, null);
+        listener.endExpressionFunctionBody(begin, null);
       }
       return token;
     } else if (optional('=', token)) {
       Token begin = token;
       // Recover from a bad factory method.
       reportRecoverableError(token, ErrorKind.ExpectedBody);
       token = parseExpression(token.next);
       if (!isExpression) {
         expectSemicolon(token);
-        listener.endReturnStatement(true, begin, token);
+        listener.endExpressionFunctionBody(begin, token);
       } else {
-        listener.endReturnStatement(true, begin, null);
+        listener.endExpressionFunctionBody(begin, null);
       }
       return token;
     }
     Token begin = token;
     int statementCount = 0;
     if (!optional('{', token)) {
       token = reportUnrecoverableError(token, ErrorKind.ExpectedFunctionBody);
       listener.handleInvalidFunctionBody(token);
       return token;
     }
@@ skipping 1508 matching lines @@
         break;
     }
     if (isRecoverable) {
       listener.handleRecoverableError(token, kind, arguments);
       return null;
     } else {
       return listener.handleUnrecoverableError(token, kind, arguments);
     }
   }
 }