title: overflow:hidden ignored with border-radius and CSS transforms (webkit only)
body: <p>I want to have a square image inside a circle.</p>
  
  <p>When the user hovers over the image, the image should scale (zoom in).</p>
  
  <p>The circle should remain the same size.</p>
  
  <p>Only during the CSS transition, the square image overlaps the circle (as if overflow:hidden weren't there at all).</p>
  
  <p>Here's a demo with the weird behavior in Chrome and Safari:
  <a href="http://codepen.io/jshawl/full/flbau">http://codepen.io/jshawl/full/flbau</a></p>
  
  <p>Working ok in firefox.</p>