Fix bug ZK-1594: Blinking popup in Firefox
http://tracker.zkoss.org/browse/ZK-1594
Fix bug ZK-1596: Invalidate component with native component inside cause JS error, zkmax only
http://tracker.zkoss.org/browse/ZK-1596
Merge branch '6.0'
Merge remote-tracking branch 'VincentJian/B60-ZK-1596' into 6.0
Merge branch '6.0'
Merge branch 'master' of github.com:jumperchen/zk