Make let variables fresh in each iteration of a for-loop.

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index 10be1707ea7d03e95bbb6f1c1b2fc954c6bb2ea5..7f9f9f230f4ffd912f1bc94e2d762c27eb75744e 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -718,6 +718,10 @@ class Parser : public ParserBase<ParserTraits> {
                                   Expression* each,
                                   Expression* subject,
                                   Statement* body);
+  Statement* DesugarLetBindingsInForStatement(
+      Scope* inner_scope, ZoneStringList* names, ForStatement* loop,
+      Statement* init, Expression* cond, Statement* next, Statement* body,
+      bool* ok);
 
   FunctionLiteral* ParseFunctionLiteral(
       Handle<String> name,