There are two ways you can get rid of the vertical scroll. First, you can turn that off in the style of the ContentPane
var cp2 = new ContentPane({
style:"overflow:hidden",
title: "Pie Chart"
});
The other way is to make the pie chart smaller
tc.watch("selectedChildWidget", function(name, oldVal, newVal){
if ( newVal.title === "Pie Chart" ) {
chart.resize(170,170);
}
});