Add an origin attribute called 'firstPartyDomain'.
This value will be extracted from the URL bar.
And the purpose of this attribute is used to isolate the data-jars.
Please see the tor documentation.
https://www.torproject.org/projects/torbrowser/design/#identifier-linkability
The idea is like a superset of 'reject third party cookies', but not
only apply for cookies, it also applies to all data-jars like localStorage,
indexedDB and so on.
So basically an iframe will have its own data-jar, and this data-jar is
isolated by the URL from URL bar, for instance, an iframe
https://facebook.com inside https://cnn.com won't share data-jar with
the iframe (https://facebook.com) in https://bbc.com
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