title: FastScroller only scrolls back to the first element, not to the header view
body: <p>I have enabled fast scrolling in a ListView, which has a not selectable headerview. If you scroll down the list and drag the fast scroll thumb to the top, the list only scrolls back to the first element, but not to the header view. Dragging the list, works as expected.  </p>
  
  <p>Screenshot1: The red area in the screenshot is the header view.<br>
  Screenshot2: If you drag the thumb to the top you get only to the  first element and the header view is still above.</p>
  
  <pre><code>ListView lv = (ListView) findViewById(R.id.listView);
  lv.addHeaderView(getLayoutInflater().inflate(R.layout.view,null), null, false);
  </code></pre>
  
  <p>&nbsp;</p>
  
  <pre><code>&lt;ListView 
     android:layout_height="fill_parent" 
     android:id="@+id/listView" 
     android:layout_width="fill_parent"
     android:fastScrollEnabled="true"
  &gt;&lt;/ListView&gt;
  </code></pre>
  
  <p>I have created a demo project: 
  <a href="https://github.com/mikegr/fastscroll-bug" rel="nofollow noreferrer">https://github.com/mikegr/fastscroll-bug</a></p>
  
  <p>Why does dragging the thumb not scroll back to the top? </p>
  
  <p><img src="https://i.stack.imgur.com/1qOYN.png" alt="Red area is a header view">
  <img src="https://i.stack.imgur.com/hlwzz.png" alt="dragging thumb does not go back to top"></p>