Update the integration test to make the file with subscription a priority one.

pkg/analysis_server/test/integration/analysis/package_root_test.dart

 // Copyright (c) 2014, 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 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:path/path.dart' as path;
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../integration_tests.dart';
@@ skipping 36 matching lines @@
     List<NavigationTarget> navigationTargets;
     List<String> navigationTargetFiles;
     onAnalysisNavigation.listen((AnalysisNavigationParams params) {
       expect(params.file, equals(mainPath));
       navigationRegions = params.regions;
       navigationTargets = params.targets;
       navigationTargetFiles = params.files;
     });
     sendAnalysisSetAnalysisRoots([projPath], [],
         packageRoots: {projPath: packagesPath});
+    sendAnalysisSetPriorityFiles([mainPath]);
     return analysisFinished.then((_) {
       // Verify that fooBarPath was properly resolved by checking that f()
       // refers to it.
       bool found = false;
       for (NavigationRegion region in navigationRegions) {
         String navigationSource =
             mainText.substring(region.offset, region.offset + region.length);
         if (navigationSource == 'f') {
           found = true;
           expect(region.targets, hasLength(1));
@@ skipping 10 matching lines @@
   }
 }
 
 @reflectiveTest
 class SetAnalysisRootsTest extends AbstractSetAnalysisRootsTest {}
 
 @reflectiveTest
 class SetAnalysisRootsTest_Driver extends AbstractSetAnalysisRootsTest {
   @override
   bool get enableNewAnalysisDriver => true;
-
-  @failingTest
-  test_package_root() {
-    //  NoSuchMethodError: The getter 'iterator' was called on null.
-    return super.test_package_root();
-  }
 }