CABaseAnimation ----keyPath取值

1.几何属性

2.背景属性

3.Layer内容(Layer Content)

4.子Layer内容(SubLayers Content)

5.边界属性(Border Attributes)

6.阴影属性(Shadow Properties)

7.透明度(Opacity Property)

8.遮罩(Mask Properties)

9.ShapeLayer属性(ShapeLayer)