Add detailed task names (#1411)
Summary:
Add the detailed task name for model background matting and super slomo.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1411
Reviewed By: aaronenyeshi
Differential Revision: D43273651
Pulled By: xuzhao9
fbshipit-source-id: ae3d88a1ce82253266dc789e47fed7eafd671607
