Reduce use of elements/resolution_types in enqueuer.

pkg/compiler/lib/src/universe/world_builder.dart

Index: pkg/compiler/lib/src/universe/world_builder.dart
diff --git a/pkg/compiler/lib/src/universe/world_builder.dart b/pkg/compiler/lib/src/universe/world_builder.dart
index 0857703be85243a049d0bbf7b26f1597fe16360c..03ce95f51f59591f7f86c5d31a53cabbdc83f1dc 100644
--- a/pkg/compiler/lib/src/universe/world_builder.dart
+++ b/pkg/compiler/lib/src/universe/world_builder.dart
@@ -156,17 +156,18 @@ abstract class WorldBuilder {
   /// constructor that has been called directly and not only through a
   /// super-call.
   // TODO(johnniwinther): Improve semantic precision.
-  Iterable<ClassElement> get directlyInstantiatedClasses;
+  Iterable<ClassEntity> get directlyInstantiatedClasses;
 
   /// All types that are checked either through is, as or checked mode checks.
-  Iterable<ResolutionDartType> get isChecks;
+  Iterable<DartType> get isChecks;
+
+  /// All directly instantiated types, that is, the types of the directly
 
   /// Registers that [type] is checked in this world builder. The unaliased type
   /// is returned.
-  ResolutionDartType registerIsCheck(ResolutionDartType type);
+  void registerIsCheck(DartType type);
 
-  /// All directly instantiated types, that is, the types of the directly
   /// instantiated classes.
   // TODO(johnniwinther): Improve semantic precision.
-  Iterable<ResolutionDartType> get instantiatedTypes;
+  Iterable<InterfaceType> get instantiatedTypes;
 }