title: backgroundImage on UIButton scales wrongly
body: <p>I'm trying to give my UIButton a new background image when the user pressed the button and then animate the width. Problem is that the button doesn't scale the image (I'm only using retina images).</p>
  
  <p><strong>Before click:</strong></p>
  
  <p><img src="https://i.stack.imgur.com/a843s.png" alt="enter image description here"></p>
  
  <p><strong>After click:</strong></p>
  
  <p><img src="https://i.stack.imgur.com/onCGf.png" alt="enter image description here"></p>
  
  <p><strong>And the code that makes things happen:</strong></p>
  
  <pre><code>UIImage *buttonProfileDefault = [[UIImage imageNamed:@"Profile_Button_Default"] resizableImageWithCapInsets:UIEdgeInsetsMake(3, 3, 3, 3)];
          [self.profileButton setBackgroundImage:buttonProfileDefault forState:UIControlStateNormal];
  
  [self.profileButton removeConstraint:self.profileButtonConstraint];
  
  // Animate
  CGRect originalFrame = self.profileButton.frame;
  originalFrame.size.width = 40;
  [UIView animateWithDuration:0.2f
      animations:^{
          self.profileButton.frame = originalFrame;
      }
          completion:^(BOOL finished) {
      }];
  </code></pre>