Strided masked var. (#68738)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/68738
Test Plan: Imported from OSS
Reviewed By: davidberard98
Differential Revision: D32767155
Pulled By: cpuhrsch
fbshipit-source-id: a5c095103405fbfc28b9f4fd624bdbbc45e7f715
