新しくなったTwitterボタンを「縦型のバルーン付きボタン」にする方法

<div class="twitter_btn">
  <a class="arrow_box" href="//twitter.com/search?q=<?php echo get_permalink(); ?>" target="_blank">リスト</a>
  <a href="https://twitter.com/share" class="twitter-share-button"{count}>Tweet</a>
  <script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0],p=/^http:/.test(d.location)?'http':'https';if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src=p+'://platform.twitter.com/widgets.js';fjs.parentNode.insertBefore(js,fjs);}}(document, 'script', 'twitter-wjs');</script>
</div>

.twitter_btn{
  width: 68px;
}

.arrow_box {
  position: relative;
  background: #fff;
  border: 1px solid #ccc;
  margin-bottom: 5px;
  text-align: center;
  font-size: 11px;
  height: 33px;
  line-height: 33px;
  display: block;
  text-decoration: none;
  color: #333;
  border-radius: 3px;
  font-family: "Hiragino Kaku Gothic ProN",Meiryo,sans-serif;
}
.arrow_box:after, .arrow_box:before {
  top: 100%;
  left: 50%;
  border: solid transparent;
  content: " ";
  height: 0;
  width: 0;
  position: absolute;
  pointer-events: none;
}

.arrow_box:after {
  border-color: rgba(255, 255, 255, 0);
  border-top-color: #fff;
  border-width: 3px;
  margin-left: -3px;
}
.arrow_box:before {
  border-color: rgba(221, 221, 221, 0);
  border-top-color: #ccc;
  border-width: 4px;
  margin-left: -4px;
}