Use AnalysisDriverUnlinkedUnit as a container for UnlinkedUnit and referenced names.

pkg/analyzer/lib/src/dart/analysis/driver.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:typed_data';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/error/error.dart';
@@ skipping 49 matching lines @@
  *
  *
  * TODO(scheglov) Clean up the list of implicitly analyzed files.
  *
  * TODO(scheglov) Handle not existing 'dart:x' URIs (while user is typing).
  */
 class AnalysisDriver {
   /**
    * The version of data format, should be incremented on every format change.
    */
-  static const int DATA_VERSION = 5;
+  static const int DATA_VERSION = 6;
 
   /**
    * The name of the driver, e.g. the name of the folder.
    */
   String name;
 
   /**
    * The scheduler that schedules analysis work in this, and possibly other
    * analysis drivers.
    */
@@ skipping 1083 matching lines @@
   @override
   int get hashCode => uri.hashCode;
 
   bool operator ==(other) {
     return other is _LibraryNode && other.uri == uri;
   }
 
   @override
   String toString() => uri.toString();
 }