Use AnalysisDriverUnlinkedUnit as a container for UnlinkedUnit and referenced names.

pkg/analyzer/test/src/dart/analysis/file_state_test.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:convert';
 import 'dart:typed_data';
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
@@ skipping 193 matching lines @@
     expect(filePackageUri.uri, packageUri);
 
     expect(fileFileUri.path, path);
     expect(fileFileUri.uri, fileUri);
 
     // The file with the `package:` style URI is canonical, and is the first.
     var files = fileSystemState.getFilesForPath(path);
     expect(files, [filePackageUri, fileFileUri]);
   }
 
+  test_referencedNames() {
+    String path = _p('/aaa/lib/a.dart');
+    provider.newFile(
+        path,
+        r'''
+A foo(B p) {
+  foo(null);
+  C c = new C(p);
+  return c;
+}
+''');
+    FileState file = fileSystemState.getFileForPath(path);
+    expect(file.referencedNames, unorderedEquals(['A', 'B', 'C']));
+  }
+
   test_refresh_differentApiSignature() {
     String path = _p('/aaa/lib/a.dart');
     provider.newFile(
         path,
         r'''
 class A {}
 ''');
     FileState file = fileSystemState.getFileForPath(path);
     expect(file.unlinked.classes[0].name, 'A');
     List<int> signature = file.apiSignature;
@@ skipping 127 matching lines @@
   void _assertTransitiveFiles(FileState file, List<FileState> expected) {
     expect(file.transitiveFiles, unorderedEquals(expected));
   }
 
   String _p(String path) => provider.convertPath(path);
 
   static String _md5(String content) {
     return hex.encode(md5.convert(UTF8.encode(content)).bytes);
   }
 }