[esnext] prototype runtime implementation for async functions

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 827857d4d0faeb2e49a6ce716a1c6f4a162e6229..615d4bf77feaa5124811a947df221b8a81c6ba40 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -951,7 +951,8 @@ enum FunctionKind {
   kClassConstructor =
       kBaseConstructor | kSubclassConstructor | kDefaultConstructor,
   kAsyncArrowFunction = kArrowFunction | kAsyncFunction,
-  kAsyncConciseMethod = kAsyncFunction | kConciseMethod
+  kAsyncConciseMethod = kAsyncFunction | kConciseMethod,
+  kArrowGeneratorFunction = kGeneratorFunction | kArrowFunction
 };
 
 inline bool IsValidFunctionKind(FunctionKind kind) {
@@ -969,7 +970,8 @@ inline bool IsValidFunctionKind(FunctionKind kind) {
          kind == FunctionKind::kSubclassConstructor ||
          kind == FunctionKind::kAsyncFunction ||
          kind == FunctionKind::kAsyncArrowFunction ||
-         kind == FunctionKind::kAsyncConciseMethod;
+         kind == FunctionKind::kAsyncConciseMethod ||
+         kind == FunctionKind::kArrowGeneratorFunction;
 }