MergeOp: Reorganize constructor and members

One injected argument for line and order by piping through `sort`;
there are just too many to think any harder about it. Other members
may have some sort of logical order to them so leave them as is for
the most part. Be consistent in assigning "this.foo = foo", which I
have been using more frequently recently. Move the @Assisted argument
last so it's obvious.

Change-Id: Idba2ebd0950c3b5cbe7ec1d08e16199dc095c097
1 file changed