gecko-dev/layout/generic/test/frame_selection_underline.css

html, body, div, span {
  margin: 0;
  padding: 0;
  line-height: 1;
}

div.selection {
  overflow: hidden;
  display: block;
  width: auto;
  height: 100px;
  white-space: nowrap;
}

div.fontsize {
  display: inline-block;
  width: auto;
  height: auto;
}

div.fontsize.size1 {
  font-size: 16px;
}

div.fontsize.size2 {
  font-size: 32px;
}

div.fontsize.size3 {
  font-size: 52px;
}

@font-face {
  font-family: "AhemTest";
  src: url(../../../fonts/Ahem.ttf);
}

@font-face {
  font-family: "mplusTest";
  src: url(../../../fonts/mplus/mplus-1p-regular.ttf);
}

div.font1,
div.font2 {
  display: inline-block;
  width: 120px;
  height: 140px;
  margin: 10px 1px;
  overflow: hidden;
}

div.font1 {
  font-family: "AhemTest";
}

div.font2 {
  font-family: "mplusTest";
}

span {
  text-align: top;
}

body.reference div.IMEselection span,
body.reference div.IMEselection span,
body.reference div.IMEselection span,
body.reference div.IMEselection span {
  background-color: black;
}