Fix issue #5398675: It's (too) easy to keep the navigation bar...

...from ever becoming visible

Now there is a 1 second delay from when the user dismisses the nav bar
until when it can be re-hidden.

Also move the code for capturing touch events while nav bar is hidden
out to be used even when there is no nav bar, so this API behaves
consistently across devices whether or not they have some element of
the UI that is being hidden.  On devices with a nav bar, this will
all work the same as prime (the flag is set, the app gets the callback
about the flag being set, when the user touches that touch is captured
so the app doesn't see it put does clear the flag and tell the app
about this).

Change-Id: Icb5ea0ddaf614aa3f12d2140796217f128761dee