Don't add files inside "packages" subdir to context.

pkg/analysis_server/test/context_directory_manager_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.
 
 library test.context.directory.manager;
 
 import 'mocks.dart';
 import 'package:analysis_server/src/context_directory_manager.dart';
 import 'package:analysis_server/src/resource.dart';
 import 'package:path/path.dart';
@@ skipping 79 matching lines @@
       String projPath = '/my/proj';
       provider.newFolder(projPath);
       String filePath = posix.join(projPath, 'foo', 'bar.dart');
       provider.newFile(filePath, 'contents');
       manager.setRoots(<String>[projPath], <String>[]);
       var filePaths = manager.currentContextFilePaths[projPath];
       expect(filePaths, hasLength(1));
       expect(filePaths, contains(filePath));
     });
 
+    test('ignore files in packages dir', () {
+      String projPath = '/my/proj';
+      provider.newFolder(projPath);
+      String pubspecPath = posix.join(projPath, 'pubspec.yaml');
+      provider.newFile(pubspecPath, 'pubspec');
+      String filePath1 = posix.join(projPath, 'packages', 'file1.dart');
+      provider.newFile(filePath1, 'contents');
+      manager.setRoots(<String>[projPath], <String>[]);
+      Set<String> filePaths = manager.currentContextFilePaths[projPath];
+      expect(filePaths, hasLength(0));
+      String filePath2 = posix.join(projPath, 'packages', 'file2.dart');
+      provider.newFile(filePath2, 'contents');
+      return pumpEventQueue().then((_) {
+        expect(filePaths, hasLength(0));
+      });
+    });
+
     group('detect context modifications', () {
       String projPath;
 
       setUp(() {
         projPath = '/my/proj';
         provider.newFolder(projPath);
       });
 
       test('Add file', () {
         manager.setRoots(<String>[projPath], <String>[]);
@@ skipping 25 matching lines @@
         manager.setRoots(<String>[projPath], <String>[]);
         Set<String> filePaths = manager.currentContextFilePaths[projPath];
         expect(filePaths, hasLength(1));
         expect(filePaths, contains(filePath));
         provider.deleteFile(filePath);
         return pumpEventQueue().then((_) => expect(filePaths, hasLength(0)));
       });
     });
   });
 }