元に戻す（塗りつぶし）のアイコン

<span class="dli-undo-fill"></span>

.dli-undo-fill {
  display: inline-block;
  vertical-align: middle;
  color: #333;
  line-height: 1;
  position: relative;
  width: 1em;
  height: 1em;
  transform: rotate(-45deg);
}

.dli-undo-fill::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: inherit;
  height: inherit;
  border: 0.1em solid currentColor;
  border-left-color: transparent;
  border-radius: 50%;
  box-sizing: border-box;
  transform: rotate(45deg);
}

.dli-undo-fill::after {
  content: '';
  position: absolute;
  top: 0.05em;
  right: 50%;
  width: 0;
  height: 0;
  border: 0.15em solid transparent;
  border-top-color: currentColor;
  border-right-color: currentColor;
  box-sizing: content-box;
  transform: translateX(-0.14142em) rotate(-135deg);
  transform-origin: top right;
}