title: How to vertically center *injected* div in HTML smoothly?
body: <p>I have a div which is perfectly centered courtesy flex. Now I inject some content dynamically into the centered div. It remains <em>centered</em> of course, but it <em>jerks</em> into that centered position, which looks downright <em>ugly</em>.</p>
  
  <p>Is there anyway to make the centering smooth? I tried setting <code>transition: all</code> but it has no effect.</p>
  
  <p>Here is a fiddle for reference and quick testing: <a href="http://jsfiddle.net/qv8fLu4n/" rel="nofollow">http://jsfiddle.net/qv8fLu4n/</a></p>