Well, if its at all possible, it would be by calling some firefox api javascript via mozrepl

So you ought to check each respective dist (mech firefoz, mozrepl obj, mozrepl, firefox ) for "history"

If you view source on ...Firefox.pm you can view sub clear_js_errors/sub js_console { for how that would work

So the searching that has to be done ddg://mozrepl clear history, ddg://site:developer.mozilla.org clear history, http://mxr.mozilla.org/firefox/search?find=%2Fbrowser%2Fbase%2Fcontent%2F&string=history