Before this commit, the save operation of wysiwyg was applied on the current editable.
After this commit, the save operation of wysiwyg can be used on a given element.
This advantage of this change is that saving can now be triggered on a copy of the original editable
element, or on any document in memory.
This makes the use case of the report editor easier to handle. That is, when the save fails, we need to
go back to the state of the editor before the save: that is WITH the changes of the user, but not cleaned by the
wysiwyg yet.
task-id-3457404
Part-of: odoo/odoo#135265
Bastien PIERRE
d5b839f713