Use GregorianCalendar.add() when searching for next alarm.

Never attribute to malice that which is adequately explained
by a bug, particularly one involving date math.

Bug: 26326394
Change-Id: I3483ac102c678a8852565c8ea94c06e19b3f26d8

packages/SystemUI/src/com/android/systemui/volume/ZenModePanel.java

@@ -511,7 +511,7 @@ public class ZenModePanel extends LinearLayout {
         GregorianCalendar weekRange = new GregorianCalendar();
         final long now = weekRange.getTimeInMillis();
         setToMidnight(weekRange);
-        weekRange.roll(Calendar.DATE, 6);
+        weekRange.add(Calendar.DATE, 6);
         final long nextAlarmMs = mController.getNextAlarm();
         if (nextAlarmMs > 0) {
             GregorianCalendar nextAlarm = new GregorianCalendar();