title: Adjust icon size of Floating action button (fab)
body: <p><img src="https://i.stack.imgur.com/N4Jzt.png" alt="Floating button">
  The new floating action button should be <strong>56dp x 56dp</strong> and the icon inside it should be <strong>24dp x 24dp</strong>. So the space between icon and button should be <strong>16dp</strong>.</p>
  
  <pre><code>&lt;ImageButton
      android:id="@+id/fab_add"
      android:layout_width="56dp"
      android:layout_height="56dp"
      android:layout_gravity="bottom|right"
      android:layout_marginBottom="16dp"
      android:layout_marginRight="16dp"
      android:background="@drawable/ripple_oval"
      android:elevation="8dp"
      android:src="@drawable/ic_add_black_48dp" /&gt;
  </code></pre>
  
  <p>ripple_oval.xml
      </p>
  
  <pre><code>&lt;ripple xmlns:android="http://schemas.android.com/apk/res/android"
      android:color="?android:colorControlHighlight"&gt;
      &lt;item&gt;
          &lt;shape android:shape="oval"&gt;
              &lt;solid android:color="?android:colorAccent" /&gt;
          &lt;/shape&gt;
      &lt;/item&gt;
  &lt;/ripple&gt;
  </code></pre>
  
  <p>And this is the result I get: <br>
  <img src="https://i.stack.imgur.com/8BVKM.png" alt="Floating button result"> <br>
  I used the icon from <em>\material-design-icons-1.0.0\content\drawable-hdpi\ic_add_black_48dp.png</em> <br>
  <a href="https://github.com/google/material-design-icons/releases/tag/1.0.1">https://github.com/google/material-design-icons/releases/tag/1.0.1</a></p>
  
  <p>How to make the <strong>size of the icon</strong> inside the button be <strong>exactly</strong> as described in guidelines ?</p>
  
  <p><a href="http://www.google.com/design/spec/components/buttons.html#buttons-floating-action-button">http://www.google.com/design/spec/components/buttons.html#buttons-floating-action-button</a></p>