extraHeight property Null safety

1. jrpn
2. view.buttons
3. CalculatorEnterButton
4. extraHeight property

CalculatorEnterButton class

1. Constructors
2. CalculatorEnterButton
3. Properties
4. acceleratorKey
5. acceleratorLabel
6. bFactory
7. extraHeight
8. fKey
9. fText
10. gKey
11. gText
12. gTextOffset
13. hashCode
14. height
15. innerBorder
16. innerBorderColor
17. key
18. keyTextOffset
19. keyTextStyle
20. lowerSurface
21. lowerSurfaceColor
22. lowerSurfaceColorPressed
23. outerBorder
24. outerBorderPressedScale
25. runtimeType
26. uKey
27. upperSurface
28. upperSurfaceColor
29. upperSurfaceColorPressed
30. uText
31. width
32. Methods
33. createElement
34. createState
35. debugDescribeChildren
36. debugFillProperties
37. drawBlueText
38. drawGoldText
39. drawKeyboardAccelerator
40. drawText
41. drawWhiteText
42. noSuchMethod
43. paintForPainter
44. toDiagnosticsNode
45. toString
46. toStringDeep
47. toStringShallow
48. toStringShort
49. Operators
50. operator ==