User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:44.0) Gecko/20100101 Firefox/44.0 Build ID: 20160210153822 Steps to reproduce: 1. Open the demo https://jsfiddle.net/uwbhddxj/9/ 2. Click run Actual results: The viewport is blank, because the <div> element has an effective height of 0. It should be a height of 100px. Expected results: Per the spec, flex elements with flex-basis of "0%", inside elements with an indefinite main-size value (like the demo's <body> element in this case), should behave like a flex-basis value of "auto". This works in Chrome, but not in Firefox. Extended debugging discussion located here: http://chat.stackoverflow.com/transcript/message/29044830#29044830
I'm unable to set the Component to Layout, that's not an option for some reason.