title: NSURLSession and NSDefaultRunLoopMode
body: <p>When using <code>NSURLConnection</code>, you had the option to schedule the connection using <code>NSRunLoop</code>:</p>
  
  <pre><code>- (void)scheduleInRunLoop:(NSRunLoop *)aRunLoop forMode:(NSString *)mode
  </code></pre>
  
  <p>Passing <code>NSDefaultRunLoopMode</code> would effectively cause the connection to pause if the user scrolled, which was great for performance as the user experience was never impacted by the download.</p>
  
  <p>Is there a way to get similar behaviour for <code>NSURLSession</code>? I have read through the docs and tried various ways of configuring the session with no success.</p>