Cleanup 1: split parts into their own libraries, remove unused imports

pkg/compiler/lib/src/types/abstract_value_domain.dart

Index: pkg/compiler/lib/src/types/abstract_value_domain.dart
diff --git a/pkg/compiler/lib/src/types/abstract_value_domain.dart b/pkg/compiler/lib/src/types/abstract_value_domain.dart
index 73e8ae405e27ebfd07b349c8c99698f59cf3c5d5..9adc8685395616f3052d167a11b57a617801b3b9 100644
--- a/pkg/compiler/lib/src/types/abstract_value_domain.dart
+++ b/pkg/compiler/lib/src/types/abstract_value_domain.dart
@@ -7,12 +7,7 @@ library dart2js.abstract_value_domain;
 import '../constants/values.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart';
-import '../native/native.dart' show
-    NativeBehavior;
-import '../universe/selector.dart' show
-    Selector;
-import '../universe/universe.dart' show
-    ReceiverConstraint;
+import '../universe/selector.dart' show Selector;
 
 enum AbstractBool {
   True, False, Maybe, Nothing