bootstrap下拉选择框倒三角所占宽度

<select id="edit" class="form-control" style="width:42%;padding-right: 3px;">
         <option selected value="CNY/USD">CNY/USD</option>
         <option value="EUR/USD">EUR/USD</option>
 </select>

form-control设置的值为12px，padding-right: 3px;将原本12px的宽度设置成3px

.form-control {

  display: block;
  width: 100%;
  height: 34px;
  padding: 6px 12px;
  font-size: 14px;
  line-height: 1.42857143;
  color: #555;
  background-color: #fff;
  background-image: none;
  border: 1px solid #ccc;
  border-radius: 4px;
  -webkit-box-shadow: inset 0 1px 1px rgba(0, 0, 0, .075);
          box-shadow: inset 0 1px 1px rgba(0, 0, 0, .075);
  -webkit-transition: border-color ease-in-out .15s, -webkit-box-shadow ease-in-out .15s;
       -o-transition: border-color ease-in-out .15s, box-shadow ease-in-out .15s;
          transition: border-color ease-in-out .15s, box-shadow ease-in-out .15s;
}