CSS dude.
I believe it is as so:
Code:::-webkit-scrollbar { /* You do this part! */ }
::-webkit-scrollbar{width:12px}
::-webkit-scrollbar-track{
-webkit-box-shadow:inset 0 0 4px rgba(0,0,0,.2);
border-radius:7px
}
::-webkit-scrollbar-thumb{
border-radius:7px;-webkit-box-shadow:inset 0 0 6px rgba(0,0,0,.4)
}