simplescrollbars.css

.CodeMirror-simplescroll-horizontal div, .CodeMirror-simplescroll-vertical div {
  position: absolute;
  -webkit-box-sizing: border-box;
     -moz-box-sizing: border-box;
          box-sizing: border-box;
  background: #ccc;
  border: 1px solid #bbb;
  border-radius: 2px;
}

.CodeMirror-simplescroll-horizontal, .CodeMirror-simplescroll-vertical {
  position: absolute;
  z-index: 6;
  background: #eee;
}

.CodeMirror-simplescroll-horizontal {
  bottom: 0;
  left: 0;
  height: 8px;
}
.CodeMirror-simplescroll-horizontal div {
  bottom: 0;
  height: 100%;
}

.CodeMirror-simplescroll-vertical {
  top: 0;
  right: 0;
  width: 8px;
}
.CodeMirror-simplescroll-vertical div {
  right: 0;
  width: 100%;
}


.CodeMirror-overlayscroll .CodeMirror-scrollbar-filler, .CodeMirror-overlayscroll .CodeMirror-gutter-filler {
  display: none;
}

.CodeMirror-overlayscroll-horizontal div, .CodeMirror-overlayscroll-vertical div {
  position: absolute;
  background: #bcd;
  border-radius: 3px;
}

.CodeMirror-overlayscroll-horizontal, .CodeMirror-overlayscroll-vertical {
  position: absolute;
  z-index: 6;
}

.CodeMirror-overlayscroll-horizontal {
  bottom: 0;
  left: 0;
  height: 6px;
}
.CodeMirror-overlayscroll-horizontal div {
  bottom: 0;
  height: 100%;
}

.CodeMirror-overlayscroll-vertical {
  top: 0;
  right: 0;
  width: 6px;
}
.CodeMirror-overlayscroll-vertical div {
  right: 0;
  width: 100%;
}