For-of statements do not permit initializers.

src/preparser.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 640 matching lines @@
   bool Check(i::Token::Value token) {
     i::Token::Value next = peek();
     if (next == token) {
       Consume(next);
       return true;
     }
     return false;
   }
   void ExpectSemicolon(bool* ok);
 
-  bool CheckInOrOf();
+  bool CheckInOrOf(bool accept_OF);
 
   static int Precedence(i::Token::Value tok, bool accept_IN);
 
   void SetStrictModeViolation(i::Scanner::Location,
                               const char* type,
                               bool* ok);
 
   void CheckDelayedStrictModeViolation(int beg_pos, int end_pos, bool* ok);
 
   void StrictModeIdentifierViolation(i::Scanner::Location,
@@ skipping 10 matching lines @@
   bool stack_overflow_;
   bool allow_lazy_;
   bool allow_natives_syntax_;
   bool allow_generators_;
   bool allow_for_of_;
   bool parenthesized_function_;
 };
 } }  // v8::preparser
 
 #endif  // V8_PREPARSER_H