[esnext] prototype runtime implementation for async functions

src/parsing/preparser.h

Index: src/parsing/preparser.h
diff --git a/src/parsing/preparser.h b/src/parsing/preparser.h
index 7379af0184f0f1d118995900a6799c75797ec9ce..23203578c23da06dda433c0f57c53ef46c7c08a4 100644
--- a/src/parsing/preparser.h
+++ b/src/parsing/preparser.h
@@ -835,8 +835,8 @@ class PreParserTraits {
   }
 
   static void AddParameterInitializationBlock(
-      const PreParserFormalParameters& parameters,
-      PreParserStatementList list, bool* ok) {}
+      const PreParserFormalParameters& parameters, PreParserStatementList list,
+      bool is_async, bool* ok) {}
 
   V8_INLINE void SkipLazyFunctionBody(int* materialized_literal_count,
                                       int* expected_property_count, bool* ok) {
@@ -853,6 +853,10 @@ class PreParserTraits {
       PreParserExpression expression, const Scanner::Location& params_loc,
       Scanner::Location* duplicate_loc, bool* ok);
 
+  void ParseAsyncArrowSingleExpressionBody(
+      PreParserStatementList body, bool accept_IN,
+      Type::ExpressionClassifier* classifier, int pos, bool* ok);
+
   V8_INLINE PreParserExpression ParseAsyncFunctionExpression(bool* ok);
 
   void ReindexLiterals(const PreParserFormalParameters& paramaters) {}