Log Message:
firefox: update to 63.0.3

    Games using WebGL (created in Unity) get stuck after very short time of \ 
gameplay (bug 1502748)
    Slow page loading for some users with specific proxy configurations (bug 1495024)
    Disable HTTP response throttling by default for causing bugs with videos in \ 
background tabs (bug 1503354)
    Opening magnet links no longer works (bug 1498934)
    Crash fixes (bug 1498510, bug 1503424)