ExtentInfo.html

<dom-module id="extent-info">

  <template>
    <div class="extent-details well">
      xmin: <span>{{xminc}}</span><br>
      ymin: <span>{{yminc}}</span><br>
      xmax: <span>{{xmaxc}}</span><br>
      ymax: <span>{{ymaxc}}</span><br>
    </div>
  </template>
  <style>
    .extent-details {
      margin: 1em;
    }
  </style>

  <script>
    var ExtentInfo = Polymer({
      is: 'extent-info',
      properties: {
        xmin: Number,
        ymin: Number,
        xmax: Number,
        ymax: Number,
        xminc: {
          type: Number,
          computed: 'toFixed(2, xmin)'
        },
        yminc: {
          type: Number,
          computed: 'toFixed(2, ymin)'
        },
        xmaxc: {
          type: Number,
          computed: 'toFixed(2, xmax)'
        },
        ymaxc: {
          type: Number,
          computed: 'toFixed(2, ymax)'
        }
      },
      toFixed: function(n, x) {
        return x.toFixed(n);
      }
    });
  </script>

</dom-module>