I worked for a company that did this years ago as a commercial tool. Also the solution worked on IE8+ with plugins for chrome and FF. Nice that Mozilla is doing the same.
Sorry. I should had explained better. That company solution didn't need plugins to work. Plugins were just an addition to the solution. And the solution also works on any mobile device with JavaScript. Funny that the company solutions is called "Cobrowse".
Well... include these snippets of code on your website means it's a plugin for your site, instead of a plugin for your browser.
Which makes a major difference if you plan to use it on mobile devices, or on desktops with no admin rights (read: office use). Also: one less thing to explain to clients.