For dijit/tests/helpers::onFocus(), if focus changes multiple times during the specified delay, return the latest focus to the callback.    Fixes a problem in the cancel test in Dialog_mouse.html: due to [23488], focus first goes to the close icon and then goes back to the button.  Perhaps the close icon should only get tabIndex=-1 when there are no focusable elements in the dialog?   For now, just changing the dijit/tests/helpers::onFocus() method.  Refs #8285 !strict.