GtkKeyHelper constructor Null safety

1. Flutter
2. services
3. GtkKeyHelper
4. GtkKeyHelper constructor

GtkKeyHelper class

1. Constructors
2. GtkKeyHelper
3. Properties
4. debugToolkit
5. hashCode
6. platformPlane
7. runtimeType
8. Methods
9. getModifierSide
10. isModifierPressed
11. logicalKey
12. noSuchMethod
13. numpadKey
14. toString
15. Operators
16. operator ==
17. Constants
18. modifierCapsLock
19. modifierControl
20. modifierMeta
21. modifierMod1
22. modifierMod2
23. modifierShift