Testcase: <!DOCTYPE html> <p style="flex-basis: 1px"></p> <script> alert(getComputedStyle(document.querySelector('p')).flexBasis); </script> It should return "1px" but it returns the initial value of flex-basis which is "auto". It seems this is expected as we haven't implemented glue for flex-basis given comment in gecko.mako.rs .  https://github.com/servo/servo/blob/66af7e4d3aeabcdecf08c8ada8cf2ed1b5ba2d64/components/style/properties/gecko.mako.rs#L459
Nazim, do you have cycles to work on this?
Sure, I can work on this!
Opened a PR in Servo: https://github.com/servo/servo/pull/15896
Nazim's PR for this landed in Servo. Nice work!