Renames and comment tweaks for files.

pkg/analyzer/test/src/dart/analysis/driver_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.
 
 library analyzer.test.driver;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 975 matching lines @@
     expect(driver.knownFiles, contains(a));
     expect(driver.knownFiles, contains(b));
   }
 
   test_knownFiles_beforeAnalysis() async {
     var a = _p('/test/lib/a.dart');
     var b = _p('/test/lib/b.dart');
 
     provider.newFile(a, '');
 
+    // 'a.dart' is added, but not processed yet.
+    // So, the set of known files is empty yet.
     driver.addFile(a);
-    expect(driver.knownFiles, contains(a));
-    expect(driver.knownFiles, isNot(contains(b)));
+    expect(driver.knownFiles, isEmpty);
 
     // Remove 'a.dart'.
     // It has been no analysis yet, so 'a.dart' is not in the file state, only
     // in 'added' files. So, it disappears when removed.
     driver.removeFile(a);
     expect(driver.knownFiles, isNot(contains(a)));
     expect(driver.knownFiles, isNot(contains(b)));
   }
 
   test_parseFile_shouldRefresh() async {
@@ skipping 491 matching lines @@
   String _p(String path) => provider.convertPath(path);
 
   Future<Null> _waitForIdle() async {
     await idleStatusMonitor.signal;
   }
 
   static String _md5(String content) {
     return hex.encode(md5.convert(UTF8.encode(content)).bytes);
   }
 }