Fixes #3100 - the problem turned out not to be in our code but instead due to this bug in FloatingActionButton which causes it to briefly appear even when made invisible. This bug doesn't occur on devices running Lollipop, but I reproduced it on 4.1 and 4.4.4.
Note that this has not been fixed in the latest version of the design support library (23), and the suggested solution in that Google issue (use the built-in show() and hide() methods) doesn't work.
So, on pre-L devices we simply don't hide the FAB or animate it in.
Only hide & animate FAB on Lollipop or higher
Couldn't get it to reproduce on my S3 with 4.1.2, but the emulator certainly showed it. Gotta love the support library 😈