Responsive Inspector Reloaded allows inspecting page media queries. Same as original, but it works on modern browsers.Original version of Responsive Inspector was broken.
https://chrome.google.com/webstore/detail/responsive-inspector-beta/memcdolmmnmnleeiodllgpibdjlkbpim
Piotr Walczyszyn (developer) stopped supporting and updating of extension. This version is open sourced and have GitHub project page: https://github.com/MistaTwista/Responsive-Inspector-Reloaded
Feel free to fork and making pull requests or add issues.
Reviews of Responsive Inspector Reloaded extension