title: customAnimation when calling popBackStack on a FragmentManager
body: <p>In my activity, with the touch of a button, I replace the current fragment with a new fragment using a custom animation, like in this example.</p>
  
  <pre><code>@Override
  public boolean onOptionsItemSelected(MenuItem item) {
      // Handle presses on the action bar items
      switch (item.getItemId()) {
          case R.id.action_anomalie:
              Fragment contentFragment = getFragmentManager().findFragmentById(R.id.content);
  
              if(contentFragment instanceof AnomalieListFragment)
              {
                  getFragmentManager().popBackStack();
                  return true;
              }
              else
              {
                  FragmentTransaction ft = getFragmentManager().beginTransaction();
                  ft.setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out);
                  anomalieFragment = new AnomalieListFragment();
                  ft.replace(R.id.content, anomalieFragment);
                  ft.addToBackStack(null);
                  ft.commit();
              }
  
      ...
  </code></pre>
  
  <p>However, <a href="http://developer.android.com/reference/android/app/FragmentManager.html#popBackStack()">popping back the stack</a> doesn't show any animation.
  Is there a way to specify a custom animation like we do in a FragmentTransaction with the <a href="http://developer.android.com/reference/android/app/FragmentTransaction.html#setCustomAnimations(int,%20int)">setCustomAnimations</a> method? </p>