I don't know how to upload pics but if I could you would have seen that the normal state of the buttons is like on your second pic. I would say you had some kind of bug for a moment when you took the 1st pic. Sometimes depending on the background the borders even disappear.
In my Moto G (running on stock android 4.4.2) Today I noticed that bottom black border looks bigger than before, on screen buttons were half covered but now its quit big, please anyone can help will be appriciate.
I uplodded Pics of before and after
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