[async-iteration] add support for for-await-of loops in Async Functions

src/parsing/preparser.h

Index: src/parsing/preparser.h
diff --git a/src/parsing/preparser.h b/src/parsing/preparser.h
index db2edf7935ec1bd788b3c45aacd1a616b7071447..9cadb62b0758c2c6de7daf037d7ebf85b427fd1f 100644
--- a/src/parsing/preparser.h
+++ b/src/parsing/preparser.h
@@ -1300,6 +1300,14 @@ class PreParser : public ParserBase<PreParser> {
     return stmt;
   }
 
+  V8_INLINE PreParserStatement InitializeForAwaitOfStatement(
+      PreParserStatement stmt, PreParserExpression each,
+      PreParserExpression iterable, PreParserStatement body, bool finalize,
+      int next_result_pos = kNoSourcePosition) {
+    MarkExpressionAsAssigned(each);
+    return stmt;
+  }
+
   V8_INLINE PreParserStatement RewriteForVarInLegacy(const ForInfo& for_info) {
     return PreParserStatement::Null();
   }