SemanticsOwner class

1. Constructors
2. SemanticsOwner
3. Properties
4. rootSemanticsNode
5. hashCode
6. hasListeners
7. runtimeType
8. Methods
9. dispose
10. performAction
11. performActionAt
12. sendSemanticsUpdate
13. toString
14. addListener
15. noSuchMethod
16. notifyListeners
17. removeListener
18. Operators
19. operator ==