Remove Legacy entry point. (#16721)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16721
The very key line is we have to set the stream to the default
stream before calling the allocator. This is very interesting.
It shouldn't be necessary, but seemingly is!
Reviewed By: dzhulgakov
Differential Revision: D13943193
fbshipit-source-id: c21014917d9fe504fab0ad8abbc025787f559287
