title: How to create HBox with only the top corners rounded in Flex?
body: <p>I'm trying to create an <code>HBox</code> in flex that has only the top corners rounded.  <code>HBox</code> (and all the other flex containers) have a <code>cornerRadius</code> style, but it applies to all corners.  I'm not seeing a way to specify the style of individual corners.</p>
  
  <p>Is there any built-in way to do this, or will I need to write my own custom drawing code to draw the background with rounded corners?</p>