[es6] allow any LeftHandSideExpression in for-of loops

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 056c011381994284826075e74d3452731579e293..788ed431fe0ac3d0193002c63e42718e68f9ef69 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -421,8 +421,7 @@ class ParserBase : public Traits {
     }
   }
 
-  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);
@@ -431,7 +430,7 @@ class ParserBase : public Traits {
         *visit_mode = ForEachStatement::ENUMERATE;
       }
       return true;
-    } else if (accept_OF && CheckContextualKeyword(CStrVector("of"))) {
+    } else if (CheckContextualKeyword(CStrVector("of"))) {
       *visit_mode = ForEachStatement::ITERATE;
       return true;
     }