code: function() {
        // take padding and border pixels from highlights div
        let padding = this.$highlights.css([
          "padding-top",
          "padding-right",
          "padding-bottom",
          "padding-left"
        ]);
        let border = this.$highlights.css([
          "border-top-width",
          "border-right-width",
          "border-bottom-width",
          "border-left-width"
        ]);
        this.$highlights.css({
          padding: "0",
          "border-width": "0"
        });
  
        this.$backdrop
          .css({
            // give padding pixels to backdrop div
            "margin-top": "+=" + padding["padding-top"],
            "margin-right": "+=" + padding["padding-right"],
            "margin-bottom": "+=" + padding["padding-bottom"],
            "margin-left": "+=" + padding["padding-left"]
          })
          .css({
            // give border pixels to backdrop div
            "margin-top": "+=" + border["border-top-width"],
            "margin-right": "+=" + border["border-right-width"],
            "margin-bottom": "+=" + border["border-bottom-width"],
            "margin-left": "+=" + border["border-left-width"]
          });
      }
docs: Firefox doesn't show text that scrolls into the padding of a textarea, so rearrange a couple box models to make highlights behave the same way