New scheme for checking function subtyping:
1) Generate an $isX predicate on objects that are statically known subtypes of a given function type
2) Generate a signature encoding the whole function type on objects when a runtime check is needed.
A check succeeds if either 1) or 2) is true.
If too many predicates are needed a signature is generated instead, and if a signature is needed, no predicates are generated. Maximum number of predicates is currently determined by the magic constant MAX_FUNCTION_TYPE_PREDICATES in emitter.dart.
R=karlklose@google.com
Review URL: https://codereview.chromium.org//12334070
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@24286 260f80e4-7a28-3924-810f-c04153c831b5
johnniwinther@google.com
2ce76ed94a