title: How to resize icon inside fab button
body: <p>I have a fab button that I would like to make smaller.  I am using <code>fabCustomSize</code> to achieve this:</p>
  
  <pre><code>&lt;android.support.design.widget.FloatingActionButton
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      app:fabCustomSize="24dp"
      android:src="@drawable/ic_add_black_24dp" /&gt;
  </code></pre>
  
  <p>However, I really want the icon to smaller than <code>24dp</code> as my button is <code>24dp</code>.</p>
  
  <p>I do realize that an easy answer probably adds a smaller icon to my app, however, I already have the <code>24dp</code> icon, is there a way to make <code>24dp</code> icon smaller?</p>