Fix tsan failure

runtime/observatory/tests/service/get_allocation_samples_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.
 // VMOptions=--error_on_bad_type --error_on_bad_override
 
 import 'dart:developer';
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/service_io.dart';
 import 'package:observatory/cpu_profile.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 49 matching lines @@
     expect(profileResponse['type'], equals('_CpuProfile'));
     await fooClass.setTraceAllocations(false);
     await fooClass.reload();
     expect(fooClass.traceAllocations, isFalse);
     CpuProfile cpuProfile = new CpuProfile();
     await cpuProfile.load(isolate, profileResponse);
     cpuProfile.buildCodeCallerAndCallees();
     cpuProfile.buildFunctionCallerAndCallees();
     var tree = cpuProfile.loadCodeTree(M.ProfileTreeDirection.exclusive);
     var node = tree.root;
-    var expected =
-        ['Root', 'DRT_AllocateObject', 'test', 'test', '_Closure.call'];
+    var expected = ['Root', 'DRT_AllocateObject', '[Stub] Allocate Foo',
+                    'test', 'test', '_Closure.call'];
     for (var i = 0; i < expected.length; i++) {
       expect(node.profileCode.code.name, equals(expected[i]));
       // Depth first traversal.
       if (node.children.length == 0) {
         node = null;
       } else {
         node = node.children[0];
       }
       expect(node, isNotNull);
     }
   },
   resumeIsolate,
 ];
 
 main(args) async => runIsolateTests(args, tests, testeeConcurrent:test);