NSViewLayerContentsRedrawCrossfade on 10.8

gistfile1.m

[NSAnimationContext runAnimationGroup:^(NSAnimationContext *context) {
    context.duration = 4.f;
    context.allowsImplicitAnimation = YES;
    
    [view.layer addAnimation:CATransition.animation forKey:@"contents"];
    view.layer.contents = someImage;
} completionHandler:nil];