Performance regression in arithmetic.ApplyIndex.time_apply_index
https://pandas.pydata.org/speed/pandas/index.html#arithmetic.ApplyIndex.time_apply_index?p-offset=%3CMonthBegin%3E&commits=55adcb8688582e3a3be66b1036d3604327ae5071-b05e6b1402124a062608b97ca02af0cfb13568d1, https://github.com/pandas-dev/pandas/compare/55adcb8688582e3a3be66b1036d3604327ae5071...b05e6b1402124a062608b97ca02af0cfb13568d1 (30 commits in there).