Update the draft filediff test suite to use the new mixins.
Review Request #4859 — Created Oct. 30, 2013 and submitted — Latest diff uploaded
Update the draft filediff test suite to use the new mixins.
The draft filediff support was written before all the new test mixins,
but committed after merging those mixins. It was never updated to use
them. This change fixes that.
Unit tests pass.