Undo/reset actions for css rules in Inspector

Currently, Inspector can see if a CSS rule was changed and shows a green left border on that rule. But unfortunately you can’t do anything about that - there’s no option to reset the rule and ctrl+z doesn’t work in Rules pane of Inspector.

Undo or Reset actions for Rules panel would reduce the need to reload the page to restore original rules, and help to save wanted changes, while removing unwanted.

This is tracked in bug 773510.