title: onActivityResult do not fire if launch mode of activity is singleInstance
body: <p>I have an Activity which is basically my main activity and its launch mode is single instance. But because of singleInstance, the <code>onActivityResult()</code> callback does not fire. And if  I change the launch mode in my manifest file to any other mode it works fine.</p>
  
  <p>Can you explain why this callback is not working?</p>