[esnext] prototype runtime implementation for async functions

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index 8da67d270091d294ff4b6343781f9e90b18ed6cc..236d70b5575bb96d80467af078b752e01994feb2 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -130,6 +130,9 @@ enum BindingFlags {
     promise_has_user_defined_reject_handler)                                  \
   V(PROMISE_REJECT_INDEX, JSFunction, promise_reject)                         \
   V(PROMISE_RESOLVE_INDEX, JSFunction, promise_resolve)                       \
+  V(PROMISE_CREATE_RESOLVED_INDEX, JSFunction, promise_create_resolved)       \
+  V(PROMISE_CREATE_REJECTED_INDEX, JSFunction, promise_create_rejected)       \
+  V(ASYNC_FUNCTION_AWAIT_INDEX, JSFunction, async_function_await)             \
   V(PROMISE_THEN_INDEX, JSFunction, promise_then)                             \
   V(RANGE_ERROR_FUNCTION_INDEX, JSFunction, range_error_function)             \
   V(REFERENCE_ERROR_FUNCTION_INDEX, JSFunction, reference_error_function)     \