anchor.diff:                      visibility: collapse !important;
                     }
                   }
  +              '';
  +            };
  +
  +            userContent = mkOption {
  +              type = types.lines;
  +              default = "";
  +              description = "Custom Firefox user content CSS.";
  +              example = ''
  +                /* Hide scrollbar in FF Quantum */
  +                *{scrollbar-width:none !important}
                 '';
               };
   
  
positive.code:             userChrome = mkOption {
                type = types.lines;
                default = "";
                description = "Custom Firefox CSS.";
                example = ''
                  /* Hide tab bar in FF Quantum */
                  @-moz-document url("chrome://browser/content/browser.xul") {
  
negative.code:             text = profile.userChrome;
            };
  
          "${profilesPath}/${profile.path}/chrome/userContent.css" =
            mkIf (profile.userContent != "") {
              text = profile.userContent;
            };
  
          "${profilesPath}/${profile.path}/user.js" =
            mkIf (profile.settings != {} || profile.extraConfig != "") {
              text = mkUserJs profile.settings profile.extraConfig;
  