message: Progress: optimzie dom struct
diff: @import './common/var.css';
  .van-progress {
  - &__bar {
  height: 4px;
  - border-radius: 4.5px;
  - width: 100%;
  - background: $c-gray-light;
  position: relative;
  + border-radius: 4px;
  + background: $c-gray-light;
  - &__finished-portion {
  - border-radius: 4.5px;
  + &__portion {
  + left: 0;
  height: 100%;
  position: absolute;
  - left: 0;
  - display: inline-block;
  + border-radius: 4px;
  }
  &__pivot {
  - padding: 2px 0;
  + top: 50%;
  + width: 28px;
  font-size: 8px;
  + margin-top: -6px;
  position: absolute;
  border-radius: 6px;
  - width: 28px;
  - background-color: $c-gray-light;
  - line-height: 8px;
  + line-height: 12px;
  text-align: center;
  - top: 50%;
  - transform: translate3d(0, -50%, 0);
  - }
  + background-color: $c-gray-light;
  }
  }
  