[es6] allow any LeftHandSideExpression in for-of loops

src/preparser.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/bailout-reason.h"
 #include "src/expression-classifier.h"
 #include "src/func-name-inferrer.h"
@@ skipping 403 matching lines @@
 
   void ExpectContextualKeyword(Vector<const char> keyword, bool* ok) {
     Expect(Token::IDENTIFIER, ok);
     if (!*ok) return;
     if (!scanner()->is_literal_contextual_keyword(keyword)) {
       ReportUnexpectedToken(scanner()->current_token());
       *ok = false;
     }
   }
 
-  bool CheckInOrOf(
-      bool accept_OF, ForEachStatement::VisitMode* visit_mode, bool* ok) {
+  bool CheckInOrOf(ForEachStatement::VisitMode* visit_mode, bool* ok) {
     if (Check(Token::IN)) {
       if (is_strong(language_mode())) {
         ReportMessageAt(scanner()->location(), MessageTemplate::kStrongForIn);
         *ok = false;
       } else {
         *visit_mode = ForEachStatement::ENUMERATE;
       }
       return true;
-    } else if (accept_OF && CheckContextualKeyword(CStrVector("of"))) {
+    } else if (CheckContextualKeyword(CStrVector("of"))) {
       *visit_mode = ForEachStatement::ITERATE;
       return true;
     }
     return false;
   }
 
   // Checks whether an octal literal was last seen between beg_pos and end_pos.
   // If so, reports an error. Only called for strict mode and template strings.
   void CheckOctalLiteral(int beg_pos, int end_pos,
                          MessageTemplate::Template message, bool* ok) {
@@ skipping 3777 matching lines @@
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PREPARSER_H