is FlowControllerImpl an unused class?

[Marshall Schor]

The interface FlowController has an abstract subclass: 
FlowController_ImplBase, which has 2 other abstract subclasses: a Cas 
and a JCas impl base.   But it also ahas a non-abstract subclass 
"FlowControllerImpl" which seems unreferenced by the rest of the code.  
Can this class be deleted?

-Marshall