ImageStreamCompleter constructor Null safety

1. Flutter
2. painting
3. ImageStreamCompleter
4. ImageStreamCompleter constructor

ImageStreamCompleter class

1. Constructors
2. ImageStreamCompleter
3. Properties
4. debugLabel
5. hashCode
6. hasListeners
7. runtimeType
8. Methods
9. addListener
10. addOnLastListenerRemovedCallback
11. debugFillProperties
12. keepAlive
13. noSuchMethod
14. removeListener
15. removeOnLastListenerRemovedCallback
16. reportError
17. reportImageChunkEvent
18. setImage
19. toDiagnosticsNode
20. toString
21. toStringShort
22. Operators
23. operator ==