Comment 1 for bug 1368817

The spec had this comment:
"The search field should empty itself if you had switched to other apps for at least five minutes "
A similar and simpler approach would be to clear it if the user goes to another application at all as they are likely done with settings.
I would not suggest clearing it when the user returns from the sub panel as I may have selected the wrong one, and would then want to select another match from the previous search.