WIP [esnext] implement async iteration proposal

src/compiler/access-builder.h

Index: src/compiler/access-builder.h
diff --git a/src/compiler/access-builder.h b/src/compiler/access-builder.h
index cbe92bae4eb5b342acf25637b3d6f93ea54c2590..eac21ee9b5f0e47801136ec86b455114eccb8ce9 100644
--- a/src/compiler/access-builder.h
+++ b/src/compiler/access-builder.h
@@ -74,6 +74,9 @@ class V8_EXPORT_PRIVATE AccessBuilder final
   // Provides access to JSGeneratorObject::input_or_debug_pos() field.
   static FieldAccess ForJSGeneratorObjectInputOrDebugPos();
 
+  // Provides access to JSAsyncGeneratorObject::await_input() field.
+  static FieldAccess ForJSAsyncGeneratorObjectAwaitInput();
+
   // Provides access to JSGeneratorObject::register_file() field.
   static FieldAccess ForJSGeneratorObjectRegisterFile();