Page parent li elements in nav menus not always given current-page-parent class

[andymacb]

Using a fresh WP3.1.1, 2010 theme, Theme Unit Test data, adding a navigation menu with Parent Page as an item without any child items and then navigating in the browser to Child Page 1.

The <li> for the parent menu item doesn't get assigned the current-page-parent class.

It does get the current-page-ancestor class, and none of my themes demand the current-page-parent class specifically so I've tagged this as trivial.