Use common.dart to re-export commonly used entities.

pkg/compiler/lib/src/serialization/modelz.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.
 
 /// Implementation of the element model used for deserialiation.
 ///
 /// These classes are created by [ElementDeserializer] triggered by the
 /// [Deserializer].
 
 library dart2js.serialization.modelz;
 
-import 'serialization.dart';
-import 'keys.dart';
+import '../common.dart';
 import '../common/resolution.dart' show
     Resolution;
 import '../compiler.dart'
     show Compiler;
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
-import '../diagnostics/source_span.dart'
-    show SourceSpan;
 import '../dart_types.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/class_members.dart' as class_members;
 import '../resolution/tree_elements.dart' show
     TreeElements;
 import '../resolution/scope.dart' show
     Scope;
 import '../script.dart';
 import '../serialization/constant_serialization.dart';
 import '../tokens/token.dart' show
     Token;
 import '../tree/tree.dart';
 import '../util/util.dart' show
     Link,
     LinkBuilder;
 
+import 'keys.dart';
+import 'serialization.dart';
+
 /// Compute a [Link] from an [Iterable].
 Link toLink(Iterable iterable) {
   LinkBuilder builder = new LinkBuilder();
   for (var element in iterable) {
     builder.addLast(element);
   }
   return builder.toLink();
 }
 
 abstract class ElementZ extends Element with ElementCommon {
@@ skipping 1512 matching lines @@
   }
 
   @override
   ElementKind get kind => ElementKind.PREFIX;
 
   @override
   Element lookupLocalMember(String memberName) {
     return _unsupported('lookupLocalMember');
   }
 }