Revert of Remove more dead code after Object.observe removal

src/runtime/runtime-function.cc

Index: src/runtime/runtime-function.cc
diff --git a/src/runtime/runtime-function.cc b/src/runtime/runtime-function.cc
index 80896e935b3773a9eb508749f07ea69f7b614c1b..939bd53e6a82799a6ce53a466fb4074a8146964c 100644
--- a/src/runtime/runtime-function.cc
+++ b/src/runtime/runtime-function.cc
@@ -280,7 +280,10 @@
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, receiver, 0);
-  return *Object::ConvertReceiver(isolate, receiver).ToHandleChecked();
+  if (receiver->IsNull() || receiver->IsUndefined()) {
+    return isolate->global_proxy();
+  }
+  return *Object::ToObject(isolate, receiver).ToHandleChecked();
 }