GestureArenaMember constructor Null safety

1. Flutter
2. gestures
3. GestureArenaMember
4. GestureArenaMember constructor

GestureArenaMember class

1. Constructors
2. GestureArenaMember
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. acceptGesture
8. noSuchMethod
9. rejectGesture
10. toString
11. Operators
12. operator ==