- renames the existing AbstractValue in cps_ir/type_propagation.dart to AbstractConstant
- introduces AbstractValue as an empty superinterface of TypeMask, and
- lift the interface of TypeMaskSystem to the superinterface AbstractValueDomain.
In follow-ups:
- change simple uses from TypeMask(System) to AbstractValue(Domain)
- update names and comment in AbstractValueDomain to more precisely reflect the abstraction
- update the complex uses (mainly type_propagation.dart) to use AbstractValue(Domain)
R=asgerf@google.com
Review URL: https://codereview.chromium.org/1415883005.
Johnni Winther
1328c98cc2