Add documentation to Vibrator on foreground/background app behavior

Add information to javadocs explaining that apps in background can only vibrate the device if the given AudioAttributes usage is one of notification, ringtone or alarm usages.

Fix: 146313440
Test: N/A
Change-Id: Iff24612ac76be6a77fbfa700ec59a2ca32b2b1b5
1 file changed