Review for Firesizer by Sanchises
Rated 2 out of 5 stars
This is included in Web Developer, including the choice between setting the size of the window or the viewport. but it's nice for non-web developers, although i don't see why they'd need it.
This review is for a previous version of the add-on (0.91).To create your own collections, you must have a Mozilla Add-ons account.