code: function interruptible(object, workFn) {
                  object._interruptibleWorkPromises = object._interruptibleWorkPromises || [];
                  var workStoredSignal = new _Signal();
                  object._interruptibleWorkPromises.push(workFn(object, workStoredSignal.promise));
                  workStoredSignal.complete();
              }
docs: These two functions manage interruptible work promises (one creates them the other cancels them). They communicate with each other thru the _interruptibleWorkPromises property which "interruptible" creates on your object.