message: Refactor how get old/new value from KVO (mac)
diff: @@ -165,14 +165,18 @@ extern void *ctx;
  {
  CGRect oldFrame = CGRectZero;
  CGRect newFrame = CGRectZero;
  - if ([change objectForKey:@"old"] != [NSNull null])
  + id oldValue = change[NSKeyValueChangeOldKey];
  + id newValue = change[NSKeyValueChangeNewKey];
  +
  + if ([oldValue respondsToSelector:@selector(CGRectValue)])
  {
  - oldFrame = [[change objectForKey:@"old"] CGRectValue];
  + oldFrame = [oldValue CGRectValue];
  }
  - if ([object valueForKeyPath:keyPath] != [NSNull null])
  + if ([newValue respondsToSelector:@selector(CGRectValue)])
  {
  - newFrame = [[object valueForKeyPath:keyPath] CGRectValue];
  + newFrame = [newValue CGRectValue];
  }
  +
  if (oldFrame.size.width != newFrame.size.width)
  {
  // HACK
  