Flex Button 设置skin后，影响combobox和ColorPicker的显示
由于button的skin属性的优先级高于combobox和colorpicker，因此如果设置了button的skin后，会影响combobox和colorpicker的显示样式。
ColorPicker
{
upSkin: ClassReference("mx.skins.halo.ColorPickerSkin");
overSkin: ClassReference("mx.skins.halo.ColorPickerSkin");
downSkin: ClassReference("mx.skins.halo.ColorPickerSkin");
disabledSkin: ClassReference("mx.skins.halo.ColorPickerSkin");
}
ComboBox
{
upSkin: ClassReference("mx.skins.halo.ComboBoxArrowSkin");
overSkin: ClassReference("mx.skins.halo.ComboBoxArrowSkin");
downSkin: ClassReference("mx.skins.halo.ComboBoxArrowSkin");
disabledSkin: ClassReference("mx.skins.halo.ComboBoxArrowSkin");
}
