Unfortunately, since this is public, you'll have to go to greater lengths to ensure binary compatibility here if you want this in 0.13.  The PR looks great to merge into the 0.14 (soon to be 1.0) branch.   However, we can't break 0.13.x users on a minor release upgrade.

I *think* (@harrah can correct me), that you can just create a secondary constructor with the previous argument values and then this should be binary compatible.  That's the  beauty of having our API be `final` :)