ImageCache constructor Null safety

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

ImageCache class

1. Constructors
2. ImageCache
3. Properties
4. currentSize
5. currentSizeBytes
6. hashCode
7. liveImageCount
8. maximumSize
9. maximumSizeBytes
10. pendingImageCount
11. runtimeType
12. Methods
13. clear
14. clearLiveImages
15. containsKey
16. evict
17. noSuchMethod
18. putIfAbsent
19. statusForKey
20. toString
21. Operators
22. operator ==