正确使用Polymer 3中的共享样式模块

:host {
  display: block;
}

.primary-button {
  background-color: #007bff;
  color: #fff;
  padding: 10px 20px;
  border-radius: 4px;
}

import { html, PolymerElement } from '@polymer/polymer/polymer-element.js';
import '@polymer/polymer/lib/elements/dom-bind.js';
import '@polymer/polymer/lib/elements/dom-repeat.js';
import '@polymer/polymer/lib/elements/dom-if.js';
import '@polymer/polymer/lib/elements/array-selector.js';
import '@polymer/polymer/lib/elements/custom-style.js';
import '@polymer/paper-button/paper-button.js';
import '@polymer/iron-icons/iron-icons.js';
import './shared-styles.js';

class MyButton extends PolymerElement {
  static get template() {
    return html`
      <style include="shared-styles">
        /* 组件自身的样式 */
        :host {
          display: block;
        }
      </style>

      <paper-button class="primary-button">Click me</paper-button>
    `;
  }
}

customElements.define('my-button', MyButton);