Using replace() is only an option with your own domain iframes. It fails to work on remote sites (eg: a twitter button) and requires some browser-specific knowledge to reliably access the child window.
Instead, just remove the iframe element and construct a new one in the same spot. History items are only created when you modify the src
attribute after it is in the DOM, so make sure to set it before the append.
Edit: JDandChips rightly mentions that you can remove from DOM, modifiy, and re-append. Constructing fresh is not required.
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