title: How to write a filtered IObservableList
body: <p>From some API call, I am getting back an <a href="http://help.eclipse.org/indigo/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fapi%2Forg%2Feclipse%2Fcore%2Fdatabinding%2Fobservable%2Flist%2FIObservableList.html" rel="noreferrer"><strong><code>IObservableList&lt;E&gt;</code></strong></a>, from the Eclipse Databinding framework. I'd wish to derive another <code>IObservableList&lt;E&gt;</code> from this one according to some predicate defined on the element type <code>E</code>. The derived list should be dynamically updated according to changes in the original list.</p>
  
  <p>How can I best implement that? I've considered subclassing <code>DecoratingObservableList</code>, but couldn't figure out how to use it.</p>
  
  <p>Of course, I could implement myself the whole <code>IObservableList</code> interface, but I was wondering if there were not other utility classes around that I could use.</p>