How can I obtain the same or similar effect in Firefox as in Chrome devtools's Layers tab?
I'd like to see what layers exist on a page and their dimensions.
It looks like FF had such feature ("3D view") but it was discontinued.
I've found and tried to use http://mozilla.github.io/layerscope/ but it doesn't seem to be what I'm looking for and I'm not sure whether it's working on FF Quantum correctly.
You may run this piece of javascript in the console. Credit goes to Chris Price. Check his article a Webkit DOM Visualizer.