title: UITextField's border flashs
body: <p>I have several <code>UITextField</code> in a scrollView,
  and I custom textFields' border by setting </p>
  
  <pre><code>layer.borderColor = ...,
  layer.borderRadius = 3.0,
  layer.borderWidth = 0.1,
  layer.masksToBounds = YES. 
  
  - (void)keyboardWillShow:(NSNotification *)notification {
  CGFloat animDuration = [notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] floatValue];
  
  CGRect rect = [self.currentTextField superview].frame;
  
  [UIView animateWithDuration:animDuration animations:^{
      [self.scrollView scrollRectToVisible:rect animated:NO];
  }];
  }
  
  - (void)keyboardWillHide:(NSNotification *)notification {
  CGFloat animDuration = [notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] floatValue];
  CGRect rect = [self.currentTextField superview].frame;
  [UIView animateWithDuration:animDuration animations:^{        
      [self.scrollView scrollRectToVisible:rect animated:NO];
  }];
  }
  </code></pre>
  
  <p>Bug every time I got any textField focused or dismiss the keyboard, all the textfield's border flashes. But if I just scroll the scrollView no flashes</p>