title: ImageButton with different states images size
body: <p>How can I prevent an <code>ImageButton</code> from having a fixed size?
  The drawables used in the selector have different size, and I want the <code>ImageButton</code> to resize itself to match the image size.</p>
  
  <p>I've tried <code>adjustViewBounds</code> without success.</p>
  
  <pre><code>&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:padding="8dp" &gt;
  
      &lt;ImageButton
          android:id="@+id/picture_imagebutton"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:adjustViewBounds="true"
          android:src="@drawable/tab_background_selector" /&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>