Fix issue with -Wunused_result and DCHECK_NOTNULL
Fix issue with -Wunused_result and DCHECK_NOTNULL

Summary: Use DCHECK instead

Reviewed By: iahs

Differential Revision: D29430980

fbshipit-source-id: f3353162bc80d9d1ac5da0d66aa1639b1ef5b1d3

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift