API REVIEW: RT-23888, Make PopupFeatures and PromptData final

[Daniel Zwolenski]

I agree with the other guys that final classes are annoying for us, but if they are needed to make things better then so be it. 

I think the emotive responses might be a result of us not knowing/understanding the benefits of the final usage and therefore only being able to assess it by its negative aspects. 

> The security problem with non-final classes has to do with attacks related to hacking finalizers, equals, hash code, and serialization from a sub class.

Can you elaborate on this? Let's say I was a malicious, Hollywood-style hacker. What kind of damage could I do and how would I do that damage via some non-final class (the 'animation' ones for example caused me much grief by being final).