message: Remove old flexbox vendor prefixes. Even IE11 supports flexbox without vendor prefixes.
diff: $min-height: 200px;
  .co-m-vert-nav {
  - // TODO: mixin for vendor prefixes.
  - display: -ms-flexbox;
  - display: -webkit-box;
  - display: -webkit-flex;
  display: flex;
  - -webkit-flex-flow: column nowrap;
  flex-flow: column nowrap;
  -
  &.co-m-pane {
  background-color: transparent;
  }
  @@ -16,19 +10,14 @@ $min-height: 200px;
  .co-m-vert-nav__menu {
  border-bottom: 1px solid $color-grey-background-border;
  - -webkit-box-flex: none;
  - -webkit-flex: none;
  flex: none;
  - font-weight: 300;
  -webkit-box-ordinal-group: 1;
  - -webkit-order: 1;
  order: 1;
  display: flex;
  padding-left: 12px;
  list-style: none;
  margin: 0;
  - background-color: rgba(255, 255, 255, 0.8);
  }
  .co-m-vert-nav-item--active {
  @@ -61,11 +50,8 @@ $min-height: 200px;
  }
  .co-m-vert-nav__body {
  - -webkit-box-flex: 1;
  - -webkit-flex: 1;
  flex: 1;
  -webkit-box-ordinal-group: 2;
  - -webkit-order: 2;
  order: 2;
  min-height: $min-height;
  