FieldSet in Viewport (bottom/right margins different than left/top, even though same)

[nbuesing]

GXT 3.0.3-SNAPSHOT 11/27 (but existed in 3.0.2 as well)
GWT 2.4.0
Windows 7 - 64 bit
Internet Explorer 8
Chrome 25

I had a FieldSet as the child of the ViewPort, and the margins used for top and left are different than the margins for bottom and right. The same behavior exists for ContentPanel, and the issue seems to happen in both IE8 and Chrome.

I would expect the margins to be the same all away around. If I didn't give margins, I wouldn't be able to see the bottom or right border at all.

Viewport viewport = new Viewport();
/* have to use a margin to be able to see the right and bottom borders, and margins are not uniform*/
viewport.add(asWidget(), new MarginData(20);
RootPanel.get().add(viewport);

ViewPortFieldSetMargins.zip