Greyson Parrelli 4952b4470d Fix bug related to gallery selection state.
TreeSets are annoying. contains() is calculated with the comparator,
which can lead to some weird bugs. Made sure the comparator didn't think
two items with the same date were identical.

Also fixed stableId generation to avoid any potential weirdness there.
2019-01-14 15:40:38 -08:00
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