title: UILabel layer cornerRadius negatively impacting performance
body: <p>I've created a document view which displays the page number in the corner.  The page number is a uilabel with a semi-transparent background colour, and has a corner radius (using the <code>cornerRadius</code> property of the <code>view</code>'s <code>layer</code>).  I've positioned this above a <code>UIScrollView</code>.  However, this makes scrolling jerky.  If I remove the <code>cornerRadius</code>, performance is good.  Is there anything I can do about this?  What would be a better solution?  It seems to have been achieved in the <code>UIWebView</code> without any performance issues.</p>