[runtime] set AsyncFunctionNext/Throw to adapt arguments

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index b96b834505c0ab62d528d74add2207a4d218e2e7..328ff63cd9d9059d22394e56a56e9a52eeb18ff4 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2466,12 +2466,12 @@ void Bootstrapper::ExportFromRuntime(Isolate* isolate,
 
       Handle<JSFunction> async_function_next =
           SimpleInstallFunction(container, "AsyncFunctionNext",
-                                Builtins::kGeneratorPrototypeNext, 2, false);
+                                Builtins::kGeneratorPrototypeNext, 1, true);
       Handle<JSFunction> async_function_throw =
           SimpleInstallFunction(container, "AsyncFunctionThrow",
-                                Builtins::kGeneratorPrototypeThrow, 2, false);
-      async_function_next->shared()->set_native(true);
-      async_function_throw->shared()->set_native(true);
+                                Builtins::kGeneratorPrototypeThrow, 1, true);
+      async_function_next->shared()->set_native(false);

[adamk, 2016/09/27 23:57:11]

I found it surprising that this was done to _keep_ the function from appearing
in stack traces. Can you explain how that works?

[caitp, 2016/09/28 00:01:18]

See IsNotInNativeScript() and IsVisibleInStackTrace() in isolate.cc

[adamk, 2016/09/28 00:03:15]

Ah, so "native" means "native but exposed to author script". Fascinating...

+      async_function_throw->shared()->set_native(false);
     }
   }
 }