[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 777f4297cb903fe950a76f8ccf8087fefb1cf56c..14086db88f7646497bd9b00c18f66c03e7878ddd 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -970,7 +970,8 @@ enum FunctionKind {
   kClassConstructor =
       kBaseConstructor | kSubclassConstructor | kDefaultConstructor,
   kAsyncArrowFunction = kArrowFunction | kAsyncFunction,
-  kAsyncConciseMethod = kAsyncFunction | kConciseMethod
+  kAsyncConciseMethod = kAsyncFunction | kConciseMethod,
+  kArrowGeneratorFunction = kGeneratorFunction | kArrowFunction
 };
 
 inline bool IsValidFunctionKind(FunctionKind kind) {
@@ -988,7 +989,8 @@ inline bool IsValidFunctionKind(FunctionKind kind) {
          kind == FunctionKind::kSubclassConstructor ||
          kind == FunctionKind::kAsyncFunction ||
          kind == FunctionKind::kAsyncArrowFunction ||
-         kind == FunctionKind::kAsyncConciseMethod;
+         kind == FunctionKind::kAsyncConciseMethod ||
+         kind == FunctionKind::kArrowGeneratorFunction;
 }
 
 
@@ -1058,6 +1060,7 @@ inline bool IsConstructable(FunctionKind kind, LanguageMode mode) {
   if (IsConciseMethod(kind)) return false;
   if (IsArrowFunction(kind)) return false;
   if (IsGeneratorFunction(kind)) return false;
+  if (IsAsyncFunction(kind)) return false;
   return true;
 }
 
@@ -1069,6 +1072,11 @@ inline uint32_t ObjectHash(Address address) {
                                kPointerSizeLog2);
 }
 
+enum class AsyncFunctionResumeMode {
+  Normal,
+  Throw,
+};
+
 }  // namespace internal
 }  // namespace v8