refactor getScale9Enabled to isScale9Enabled
refactor UIButton
refactor ImageView
refactor Slider control
refactor loadingBar
refactor Layout
fix minor bugs of UISlider and remove unused header include in ListView
refactor, improve imageView stability
refactor, optimize Scale9Sprite
Merge pull request #7627 from andyque/fixScale9Sprite

refactor ui::widgets to use ui::Scale9Sprite instead of extension::Scale9Sprite