Background is not a gradient when compiling a Flex 3 app. with Flex 4 and using the halo theme.

Steps to reproduce:
1. Compile this:
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" />

with this command:

mxmlc -theme=path_to_sdk/frameworks/themes/Halo/halo.swc test.mxml

Actual Results:
The background colors do not form a gradient.

Expected Results:
They should.

Workaround (if any):
A couple options:
1. Set the backgroundGradientColors style yourself.
2. Compile with -compatibility-version=3.0. (But this, of course, puts you back in 3.x.)