title: Why UIBarButtonItem's foucs area smaller than prior in iOS11?
body: <pre><code>UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];  
  [button setImage:[UIImage imageNamed:@"back"] forState:UIControlStateNormal];  
  [button sizeToFit];  
  [button setBackgroundColor:[UIColor greenColor]];  
  [button addTarget:self  
             action:@selector(tap)  
   forControlEvents:UIControlEventTouchUpInside];  
  self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:button]; 
  </code></pre>
  
  <p>When i run in iOS 10 or prior version, I can touch outside this button's bounds more than 5-10px and trigger this action(tap).</p>
  
  <p>But in new released iOS11, I can trigger action only touch inside the area.</p>
  
  <p>How can I do like the performance in iOS10 or prior?
  Is the new layout of new navigationItem lead to this question?</p>