Calling dismiss() should trigger onFinish call

[yizaho]

We would like to allow the user to finish the showcase at anytime by tapping a FloatingActionWidget close button.

When tapping this close button, we call dismiss, and the showcase appears to end, but onFinish is not called. It is important for onFinish to be called, since we have critical operations that need to be executed there (e.g. re-enabling taps/gestures).

Therefore, we would assume (hope) dismiss would also trigger onFinish.

We've tried using dismiss + next, but ids are null.

Currently, as a workaround, we are running a completed loop on the remaining keys, but this isn't ideal. It would be easier if dismiss() triggers onFinish.