Move dart2jslib parts into separate libraries.

pkg/compiler/lib/src/serialization/modelz.dart

Index: pkg/compiler/lib/src/serialization/modelz.dart
diff --git a/pkg/compiler/lib/src/serialization/modelz.dart b/pkg/compiler/lib/src/serialization/modelz.dart
index 8bf7a9f159dfd05a9ae9f1d9842bede4addf803e..5f74d50f5cf60b8d5654616d3984dbc027c9f715 100644
--- a/pkg/compiler/lib/src/serialization/modelz.dart
+++ b/pkg/compiler/lib/src/serialization/modelz.dart
@@ -16,21 +16,21 @@ import '../constants/expressions.dart';
 import '../dart2jslib.dart'
     show Backend,
          Compiler,
-         DiagnosticListener,
-         Script,
          SourceSpan;
 import '../dart_types.dart';
+import '../diagnostic_listener.dart';
 import '../elements/elements.dart';
 import '../elements/modelx.dart' show FunctionSignatureX;
 import '../elements/common.dart';
 import '../elements/visitor.dart';
+import '../io/source_file.dart';
 import '../ordered_typeset.dart';
 import '../resolution/resolution.dart';
 import '../resolution/class_members.dart' as class_members;
 import '../resolution/enum_creator.dart' show AstBuilder;
 import '../scanner/scannerlib.dart' show Token, SEMICOLON_INFO;
+import '../script.dart';
 import '../serialization/constant_serialization.dart';
-import '../io/source_file.dart';
 import '../tree/tree.dart';
 import '../util/util.dart' show Link, LinkBuilder;