Cloud Icon in Notification Bar -- Duplicate Photos?

I had a cloud icon appear in my notification bar this morning with a loading bar that was at 6%. It said that it was checking for duplicate photos. When I clicked it asked if I wanted to wait and gave me the options "OK" or "Cancel".

I couldn't figure out what this was or where it was looking for duplicate photos (phone or cloud).

Anyone experience this or know what it is?

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