Fix legacy const for-of/in destructuring

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index f122d9aa5e4b57ff1459cfa48e060c666bd407ff..c241375535bf1a9f40e79433fa477feefbf21272 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -2593,7 +2593,9 @@ void Parser::ParseVariableDeclarations(VariableDeclarationContext var_context,
     }
 
     // Make sure that 'const x' and 'let x' initialize 'x' to undefined.
-    if (value == NULL && parsing_result->descriptor.needs_init) {
+    // If in a for-of/in loop, no need to initialize here.
+    if (value == NULL && parsing_result->descriptor.needs_init &&
+        !is_for_iteration_variable) {
       value = GetLiteralUndefined(position());
     }