Make the universe parts into small libraries.

pkg/compiler/lib/src/cps_ir/type_mask_system.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.type_mask_system;
 
 import '../closure.dart' show ClosureClassElement, Identifiers;
 import '../common/names.dart' show Selectors, Identifiers;
 import '../compiler.dart' as dart2js show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../dart_types.dart' as types;
 import '../elements/elements.dart';
 import '../io/source_information.dart' show SourceInformation;
 import '../js_backend/js_backend.dart' show JavaScriptBackend;
 import '../types/types.dart';
 import '../types/constants.dart' show computeTypeMask;
-import '../universe/universe.dart';
+import '../universe/selector.dart' show Selector;
 import '../world.dart' show World;
 
 enum AbstractBool {
   True, False, Maybe, Nothing
 }
 
 class TypeMaskSystem {
   final TypesTask inferrer;
   final World classWorld;
   final JavaScriptBackend backend;
@@ skipping 260 matching lines @@
     }
     return dynamicType;
   }
 
   /// Returns a subset of [mask] containing at least the types
   /// that can respond to [selector] without throwing.
   TypeMask receiverTypeFor(Selector selector, TypeMask mask) {
     return classWorld.allFunctions.receiverType(selector, mask);
   }
 }