Refactor and reorganize type inference classes before porting ConcreteTypesInferrer to InferrerVisi…

sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart

Index: sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart b/sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart
index ab7226bb5e695acc1251f3f7e16de067a1ae98e8..c13d7a4b3c09c2c827064e8eb2cdaf53ab9455c6 100644
--- a/sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart
+++ b/sdk/lib/_internal/compiler/implementation/types/concrete_types_inferrer.dart
@@ -2,7 +2,18 @@
 // 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.
 
-part of types;
+library concrete_types_inferrer;
+
+import 'dart:collection' show Queue, IterableBase;
+import '../dart2jslib.dart' hide Selector, TypedSelector;
+import '../dart_types.dart';
+import '../elements/elements.dart';
+import '../native_handler.dart' as native;
+import '../tree/tree.dart';
+import '../universe/universe.dart';
+import '../util/util.dart';
+
+import 'types.dart' show TypeMask, TypesInferrer;
 
 class CancelTypeInferenceException {
   final Node node;