message: Tightens margin on dropdowns
diff: position absolute
  left 50%
  bottom 0
  - transform translate(-50%, 200%)
  + transform translate(-50%, 100%)
  border-bottom (size / 2) solid colors-gray-border
  border-right (size / 3) solid transparent
  border-left (size / 3) solid transparent
  display none
  position fixed
  top topbar_h + dropdown-border-width
  - margin-top 1em
  + margin-top 0.5em
  right 1em
  z-index dropdown_z
  font-weight normal
  