Refactor groups to pipe them through to the runner.

lib/src/runner/vm/isolate_test.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.runner.vm.isolate_test;
 
 import 'dart:async';
 import 'dart:isolate';
 
 import '../../backend/live_test.dart';
 import '../../backend/live_test_controller.dart';
 import '../../backend/metadata.dart';
+import '../../backend/operating_system.dart';
 import '../../backend/state.dart';
 import '../../backend/suite.dart';
 import '../../backend/test.dart';
+import '../../backend/test_platform.dart';
 import '../../util/remote_exception.dart';
 import '../../utils.dart';
 
 /// A test in another isolate.
-class IsolateTest implements Test {
+class IsolateTest extends Test {
   final String name;
   final Metadata metadata;
 
   /// The port on which to communicate with the remote test.
   final SendPort _sendPort;
 
   IsolateTest(this.name, this.metadata, this._sendPort);
 
-  /// Loads a single runnable instance of this test.
   LiveTest load(Suite suite) {
     var controller;
 
     // We get a new send port for communicating with the live test, since
     // [_sendPort] is only for communicating with the non-live test. This will
     // be non-null once the test starts running.
     var sendPortCompleter;
 
     var receivePort;
     controller = new LiveTestController(suite, this, () {
@@ skipping 38 matching lines @@
         // whenever the test touches it.
         var sendPort = await sendPortCompleter.future;
         sendPort.send({'command': 'close'});
         await controller.completer.future;
         receivePort.close();
       });
     });
     return controller.liveTest;
   }
 
-  Test change({String name, Metadata metadata}) {
-    if (name == name && metadata == this.metadata) return this;
-    if (name == null) name = this.name;
-    if (metadata == null) metadata = this.metadata;
-    return new IsolateTest(name, metadata, _sendPort);
+  Test forPlatform(TestPlatform platform, {OperatingSystem os}) {
+    if (!metadata.testOn.evaluate(platform, os: os)) return null;
+    return new IsolateTest(
+        name, metadata.forPlatform(platform, os: os), _sendPort);
   }
 }