title: Using ng-content to select base class
body: <p>Suppose I have a component <code>Parent</code> that content projects <code>Child</code> components as follows. In this case, <code>Child</code> is an abstract base class that is extended by components <code>ChildA</code> and <code>ChildB</code>. Here's an example use cased in a user's template:</p>
  
  <pre><code>&lt;parent&gt;
    &lt;child-a&gt;&lt;/child-a&gt; // or child-b
  &lt;/parent&gt;
  </code></pre>
  
  <p>In the <code>Parent</code>'s template I want to use <code>&lt;ng-content&gt;</code> to content project the <code>Child</code> component.  However, I want to be able to use <code>&lt;ng-content&gt;</code> and somehow select either the <code>&lt;child-a&gt;</code> or <code>&lt;child-b&gt;</code>, something like:</p>
  
  <pre><code>&lt;ng-content select="child-a | child-b"&gt;&lt;/ng-content&gt;
  </code></pre>
  
  <p>Is there a way to do this?</p>