Created Unassigned: Inheriting DefaultHttpControllerActivator [1713]

Currently you can inherit `System.Web.Http.Dispatcher.DefaultHttpControllerActivator` but can't override `Create()` because it [isn't marked](http://msdn.microsoft.com/en-us/library/hh944283%28v=vs.118%29.aspx) `virtual`.
Please make it possible. Thanks!