Before this commit, pasting html content that had been copied from the
the Editor failed to paste any content when inside an iframe.
This happened because the DOMPurify library was not configured to use
the iframe's window for Node prototypes, which led `instanceof` checks
to fail, removing nodes a result.
Additionally, commit [1] did not do the job completely: while the
document for creating the document fragment became the one received as
parameter, the DOMParser constructor remained the one from the window in
which the JS code is executed, which might be different from the
received document's window. This mismatch happens in particularly when
the editable is inside an iframe.
task-3575496
[1]: https://github.com/odoo/odoo/commit/c74d01279e49fadc5f509cfc3f6baf43d2b532d1closesodoo/odoo#144744
Signed-off-by: Geelen Sébastien (sge) <sge@odoo.com>