0.
dart --observe retainingPath.dart
1.
isolate 'root'
2.
library 'retainingPath.dart'
3.
class 'Foo'
4.
under 'instances', find 'strongly reachable' list; it should contain 2 elements, one of which should have a field containing "87"
5.
instance "87"
6.
find 'retaining path'; it should have length 4, and be annotated as follows:
 "87" in var a
 Foo in var b
 Foo at list index 5 of
 _List(10)