palemoon-dev/platform/layout/reftests/forms/input/file/style.css

vbox, hbox {
  margin-top: 8px;
  margin-left: 8px;
  display: block;
}

.file {
  /* Copy of input properties that apply of forms.css below this */
  color: inherit;
  font: -moz-field;
  text-rendering: optimizeLegibility;
  line-height: normal !important;
  text-align: start;
  text-transform: none;
  word-spacing: normal;
  letter-spacing: normal;
  text-indent: 0;
  -moz-user-select: text;
  text-shadow: none;

  /* Copy of the type=file part of forms.css below this */
  display: inline; /* this one isn't really a copy... */
  white-space: nowrap;
  overflow:hidden;

  -moz-appearance: none;
  -moz-binding: none;
  cursor: default;
  border: none;
  background-color: transparent;
  padding: 0;
}

.file > label {
  display: inline-block;

  /* Copy from forms.css below this */
  min-width: 12em;
  padding-inline-start: 5px;

  color: inherit;
  font-size: inherit;
  letter-spacing: inherit;

  direction: ltr !important;
}

.file[dir='rtl'] > label {
  /* Copy from forms.css below this */
  padding-inline-start: 0px;
  padding-right: 5px;
  text-align: right;
}

.file > button {
  /* Copy from forms.css below this */
  height: inherit;
  font-size: inherit;
  letter-spacing: inherit;
  cursor: inherit;
}