In my case, I want to dubug bootstrap tooltip. But the methods above not work for me. I guess bootstrap implemented this by something like mouse in/out event.
Anyway, when I hover on a button, it will generate a brother html element below the button, so I select the button's parent element in "Elements" tab of "Developer tools" window, hover the button, and "Ctrl + C", then I can paste the source code which contains the generated code. Last find the generated code, and add it to the source code by "Edit as HTML" in "Elements" tab.
Hope it can help somebody.