How do I identify what addon a UI element belongs to?

The command you are looking for is:

/framestack

Just to let you know, I found the dreaded addon that does this horrible action of placing dot timer bars right in front of your character. The addon is CLASSTIMER.

https://mods.curse.com/addons/wow/classtimer

This is a huge flaw in the UI design because it takes FOREVER to find this addon, even with /framestack or /fstack.

And yes, even in 2017 the addon has the SAME BEHAVIOUR. :S

Solution: delete addon