[esnext] prototype runtime implementation for async functions

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 936cf40a3b0aa6c8dac298256f86be6a94811e0a..54edf377bc044bcf7b19c409c612aba7a8ccfed8 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2370,6 +2370,13 @@ void Bootstrapper::ExportFromRuntime(Isolate* isolate,
           script_is_embedder_debug_script, attribs);
       script_map->AppendDescriptor(&d);
     }
+
+    {
+      SimpleInstallFunction(container, "AsyncFunctionNext",
+                            Builtins::kAsyncFunctionNext, 2, false);
+      SimpleInstallFunction(container, "AsyncFunctionThrow",
+                            Builtins::kAsyncFunctionThrow, 2, false);
+    }
   }
 }