Bug 139381 – ::-webkit-scrollbar continues to not support transitions

• Component: Animations
• Status: RESOLVED WONTFIX

[Sean Anderson]

Transitions became supported on pseudo-selectors fairly recently. However, transitions do not appear to be supported on the ::-webkit-scrollbar (et. al) selectors.

I expect background-color to transition when hovering over a scrollbar with a transition applied to it.

Example: http://codepen.io/Meo/pen/EaPvwV

Code: 

<div class='parent'>
  <div class='child'>
  </div>
</div>

.parent {
  height: 100px;
  width: 100px;
  overflow-y: scroll;
  overflow-x: hidden;
}

.child {
  width: 200px;
  height: 200px;
}

::-webkit-scrollbar {
  width: 8px;
}

::-webkit-scrollbar-thumb {
  transition: all 5s linear;
  -webkit-transition: all 5s linear;
  background-color: blue;
}

::-webkit-scrollbar-thumb:hover {
  background-color: gray;
}

[Antoine Quint]

I don't think we want to add support for transitions for ::-webkit-scrollbar or generally improve that feature. Marking as WONTFIX.