I have a problem with embedded firefox XML viewer and debug functional in dev tools when the extension is enabled.
Firefox can not parse XML and view him as an HTML page without tags, only text values.
When I add "debugger;" in my code, then dev tools catch breakpoint, but he can't display source file, debug steps work, but I can not see where they step. Links to bug line from console to source code do not work.
In most cases a very good extension, but in some case, you will have a problem with web development. (((