Use common Comparator.

Every AlarmPriorityQueue will use the exact same comparator, so there's
no point creating a new one for each instance.

Bug: 247097209
Test: atest FrameworksMockingServicesTests:AlarmQueueTest
Change-Id: I8e07157fef57f6047414e9c8b46da0dac91c6714
1 file changed