无JIRA fix: checkbox的自适应

src/less/base/single/input/checkbox.less

@@ -9,14 +9,13 @@
     &:after {
       position: absolute;
       display: table;
-      // 百分比会出现像素误差
+      top: 45%;
-      top: 6px;
+      left: 20%;
-      left: 2px;
       border: 2px solid transparent;
       border-top: 0;
       border-left: 0;
-      width: 6px;
+      width: 50%;
-      height: 9px;
+      height: 75%;
       .box-sizing(border-box);
       .transform(rotate(45deg) scale(1) translate(-50%, -50%));
       @transition: all .1s cubic-bezier(.71, -.46, .88, .6), opacity .1s;