title: Angular-Material "md-datepicker" directive - "md-open-on-focus" issue
body: <p>As exampled in this <a href="https://jsfiddle.net/goueo40n/2/" rel="nofollow noreferrer">fiddle</a>, there's seems to be an inconsistency issue with opening the <code>md-datepicker</code> multiple times when using <code>md-open-on-focus</code>.</p>
  <p>The problem occurs after opening and closing it for the first time (which works ok) - after that, it'll randomly open on click and become unstable.</p>
  <pre><code>&lt;md-datepicker ng-model=&quot;timeModel&quot; md-hide-icons=&quot;all&quot; md-open-on-focus&gt;&lt;/md-datepicker&gt;
  </code></pre>
  <p>Has anyone experienced the same behavior and found a solution? Thanks.</p>