Make Suite contain a single Group.

lib/src/backend/group_entry.dart

 // Copyright (c) 2015, 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.backend.test_or_group;
+library test.backend.group_entry;
 
 import 'metadata.dart';
 import 'operating_system.dart';
 import 'test.dart';
 import 'test_platform.dart';
 
 /// A [Test] or [Group].
-abstract class SuiteEntry {
-  /// The name of the entry, includes the prefixes from any containing [Group]s.
+abstract class GroupEntry {
+  /// The name of the entry, including the prefixes from any containing
+  /// [Group]s.
+  ///
+  /// This will be `null` for the root group.
   String get name;
 
   /// The metadata for the entry, including the metadata from any containing
-  /// [Group]s and the test suite.
+  /// [Group]s.
   Metadata get metadata;
 
   /// Returns a copy of [this] with all platform-specific metadata resolved.
   ///
   /// Removes any tests and groups with [Metadata.testOn] selectors that don't
   /// match [platform] and [selector]. Returns `null` if this entry's selector
   /// doesn't match.
-  SuiteEntry forPlatform(TestPlatform platform, {OperatingSystem os});
+  GroupEntry forPlatform(TestPlatform platform, {OperatingSystem os});
 
   /// Returns a copy of [this] with all tests that don't match [callback]
   /// removed.
   ///
   /// Returns `null` if this is a test that doesn't match [callback] or a group
   /// where no child tests match [callback].
-  SuiteEntry filter(bool callback(Test test));
+  GroupEntry filter(bool callback(Test test));
 }