chart-styles.html

<dom-module id="chart-styles">

  <template>

    <style>
      :host {
        display: inline-block;
        position: relative;
      }

      :host > div {
        height: 100%;
      }

      #canvas {
        width: 100%;
        height: 100%;
      }
    </style>

  </template>

</dom-module>