_writeStyleToken(tok) {
    const el = this._buildStyle(tok);

    this._insertCursor(el, PROXY_STYLE);

    // Set content
    if (tok.content) {
      if (el.styleSheet && !el.sheet) {
        el.styleSheet.cssText = tok.content;
      } else {
        el.appendChild(this.doc.createTextNode(tok.content));
      }
    }
  }
Build a style and insert it into the DOM.

@param {Object} tok The token