When does Chrome pass a value other then 0 to the native messaging host for --parent-window? - google-chrome

Question

I am developing a Chrome extension on windows. It also has a native messaging host. The argument passed to the host named --parent-window is in my case always 0.
According to the Native Messaging Protocol it says
On Windows, the native messaging host is also passed a command line
argument with a handle to the calling chrome native window:
--parent-window=. This lets the native messaging host create native UI windows that are correctly focused.
I open my port for native messaging in the background JS. My understanding is that you cannot use this API in content.
This Chromium Bug appears to be my issue but it was closed as a won't fix.
So when or in what circumstances does Chrome send something useful with the --parent-window?
Further on May 7 the writer who I assume knows a bit about chromium says
Haven't tried it, but could you open your native messaging port in a
content script instead? Sounds like the --parent-window arg might be
useful in that case.
What does he mean and how do I do this?

Answer 1

Answering my own question. In short it does not work as you would expect if you are a windows developer. Possibly comment 2 helps from the "Wont Fix" issue on Chromium.
Comment 2 seems to explain when it might work.
If you are using Native Messaging
(https://developer.chrome.com/extensions/messaging#native-messaging),
it would seem like the --parent-window command line parameter would
provide a solution. Unfortunately, zero is passed for the parent
window if the native messaging connection is made from a background
page and (apparently) the HWND of a transient popup window is passed
if the native messaging connection is made from a browser action
popup. And I am not allowed to call chrome.runtime.connectNative()
from a content script. Therefore, in my extension at least,
--parent-window is not helpful.
My solution is immediately after
port = chrome.runtime.connectNative('myspecial.host.application');
I then use the following;
chrome.tabs.query({ active: true, currentWindow: true }, function (tab) {
console.log(tab[0].title);
port.postMessage({ MessageType: 'chromeTitle', Message: tab[0].title });
});
In your host if you add to this titel " - Google Chrome" then you can call FindWindowEX with the class "Chrome_WidgetWin_1" and the title to get the main handle of Google.