As another double check that the patch worked as expected, I wrote a patch to log when we add a message listener or receive a message manager message, in the parent process. I tested starting the browser with "open previous tabs" enabled with a few tabs saved. On MacOS desktop, without the patch, we register 5 message listeners with "SessionStore" in the name. With the patch, we don't have any. So that is working as expected.
Bug 1886852 Comment 6 Edit History
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As another double check that the patch worked as expected, I wrote a patch to log when we add a message listener or receive a message manager message, in the parent process. I tested starting the browser with "open previous tabs" enabled with a few tabs saved. On MacOS desktop, without the patch, we register 5 message listeners with "SessionStore" in the name. With the patch, we don't have any. So that is working as expected. Also as expected, in this simple scenario we don't receive any messages with SessionStore in the name, both with and without the patch.