Move dart2jslib parts into separate libraries.

pkg/compiler/lib/src/inferrer/inferrer_visitor.dart

Index: pkg/compiler/lib/src/inferrer/inferrer_visitor.dart
diff --git a/pkg/compiler/lib/src/inferrer/inferrer_visitor.dart b/pkg/compiler/lib/src/inferrer/inferrer_visitor.dart
index e4725b2d9df52d7e3a7832a1d86b1c93cf7bb1db..093e229130492185ffe63e47425c7feb07b61639 100644
--- a/pkg/compiler/lib/src/inferrer/inferrer_visitor.dart
+++ b/pkg/compiler/lib/src/inferrer/inferrer_visitor.dart
@@ -4,18 +4,21 @@
 
 library inferrer_visitor;
 
+import 'dart:collection' show IterableMixin;
+
 import '../constants/constant_system.dart';
 import '../constants/expressions.dart';
 import '../dart2jslib.dart' hide Selector, TypedSelector;
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../resolution/operators.dart';
+import '../resolved_visitor.dart';
 import '../tree/tree.dart';
-import '../universe/universe.dart';
-import '../util/util.dart';
 import '../types/types.dart' show TypeMask;
 import '../types/constants.dart' show computeTypeMask;
-import 'dart:collection' show IterableMixin;
+import '../universe/universe.dart';
+import '../util/util.dart';
+import '../world.dart' show ClassWorld;
 
 /**
  * The interface [InferrerVisitor] will use when working on types.