Make the universe parts into small libraries.

tests/compiler/dart2js/gvn_dynamic_field_get_test.dart

 // Copyright (c) 2012, 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.
 // Test that dart2js gvns dynamic getters that don't have side
 // effects.
 
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'compiler_helper.dart';
-import 'package:compiler/src/universe/universe.dart' show Selector;
+import 'package:compiler/src/universe/selector.dart' show Selector;
 
 const String TEST = r"""
 class A {
   var foo;
   bar(a) {
     return a.foo + a.foo;
   }
 }
 
 main() {
@@ skipping 11 matching lines @@
     checkNumberOfMatches(matches, 1);
     var cls = findElement(compiler, 'A');
     Expect.isNotNull(cls);
     String name = 'foo';
     var element = cls.lookupLocalMember(name);
     Expect.isNotNull(element);
     Selector selector = new Selector.getter(name, null);
     Expect.isFalse(compiler.world.hasAnyUserDefinedGetter(selector, null));
   }));
 }