title: getting a subview's WINDOW coordinates issue with convertRect
body: <p>from main viewController's <strong>ViewDidAppear</strong></p>
  
  <pre><code>UIView* parent = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
  UIView* child1 = [[UIView alloc] initWithFrame:CGRectMake(30, 30, 60, 60)];
  UIView* child2 = [[UIView alloc] initWithFrame:CGRectMake(10, 10, 20, 20)];
  
  [parent setBackgroundColor:[UIColor redColor]];
  [child1 setBackgroundColor:[UIColor blackColor]];
  [child2 setBackgroundColor:[UIColor greenColor]];
  
  [child1 addSubview:child2];
  [parent addSubview:child1];
  [self.view addSubview:parent];
  
  NSLog(@"Absolute coordinates of child2: %@",NSStringFromCGRect([child2 convertRect:child2.frame toView:nil] ));
  </code></pre>
  
  <p><strong>abs point of child2: {{150, 170}, {20, 20}}</strong></p>
  
  <p>I was expecting the origins to be (140,140, 20,20).</p>
  
  <p>Why the extra 10 for the <code>X</code> and 30 for the <code>Y</code>?</p>