No frames!!!

Basically use something like

$load = $mech->repl->declare(<<'__JS');
  function () {
     // start benchmark
     window.content.location.href = "http://www.perlmonks.org";
     // wait till ready (can be tricky)
     // stop benchmark
     // return diff
  }
__JS
[download]

and $load->() should load the page.