If you use http://www.sublimetext.com/ you will get a dialog when scripts are running slow, as in, "Script XYZ took more than 1 second to process this file, you can disable it"
All I want in FF or Chrome is the same.
"Adblock blocked the UI for 4 seconds" "Adblock increased memory consumption by double"
Or they could even be more harsh and kill plugins that take too long and impact user experience like the Flash timeout.