dart2js: accept const map literals as expression statements.

pkg/compiler/lib/src/scanner/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.
 
 part of scanner;
 
 class FormalParameterType {
   final String type;
   const FormalParameterType(this.type);
   bool get isRequired => this == REQUIRED;
@@ skipping 1552 matching lines @@
     Token peek = peekAfterType(token);
     if (peek != null && peek.isIdentifier()) {
       // We are looking at "type identifier".
       return peek;
     } else {
       return null;
     }
   }
 
   Token peekIdentifierAfterOptionalType(Token token) {
-    Token peek = peekIdentifierAfterType(token);
-    if (peek != null) {
+    Token peek = peekAfterIfType(token);
+    if (peek != null && peek.isIdentifier()) {
       // We are looking at "type identifier".
       return peek;
     } else if (token.isIdentifier()) {
       // We are looking at "identifier".
       return token;
     } else {
       return null;
     }
   }
 
@@ skipping 1008 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }