GH-6530: Set the shutdown hook to beforeunload.

[kittaakos]

• unload was not triggered in electron. (See: window unload event does not fire electron/electron#7278 (comment))
• Exposed ShellLayoutRestorer APIs.
• Added logging.
• Fixed typos.

Closes #6530.

Signed-off-by: Akos Kitta [email protected]

What it does

This PR moves the frontend application's shutdown hook from unload to beforeunload as it the master state does not work with the electron example.

How to test

• Build the electron example from the source,
• refresh the browser a few times,
• check the logs,
• you can see the layout is stored. ✨

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[akosyakov]

We need to test the browser example as well.

[vince-fugnitto]

I verified both the electron and browser targets:

• created a complex layout, performed reload and the layout was successfully restored.
• logs successfully adds detail about the state of the application.

Are there any other use cases I need to validate?

[vince-fugnitto]

I'm happy with the changes :)
We get more information about the state of the application when reloading, and restoring layout works correctly on both targets.

[kittaakos]

I am going to merge this tomorrow, please object if you want.