Changes

We have a specific tool helping us to find when the code that introduced a regression landed in Nightly, this is called [https://mozilla.github.io/mozregression/ mozegression].  There is a GUI for Windows and a command line interface for Linux/Mac.Here is an article on * Article about the Nightly blog about itCLI version: [https://blog.nightly.mozilla.org/2016/10/11/found-a-regression-in-firefox-give-us-details-with-mozregression/ Found a regression in Firefox? Give us details with mozregression!]* Article with a video tutorial about the Windows version: [https://blog.nightly.mozilla.org/2017/06/07/using-mozregression-on-windows/ Using mozregression on Windows]