Mark test as flaky

runtime/tests/vm/vm.status

 # Copyright (c) 2012, 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.
 
 # These tests are expected to crash on all platforms.
 cc/ArrayNew_Overflow_Crash: Crash
 cc/AllocGeneric_Overflow: Crash
 
 cc/SNPrint_BadArgs: Skip
 
 # These tests are skipped because of the workaround to open issue 8594.
 cc/Debug_StackTraceDump1: Skip
 cc/Debug_StackTraceDump2: Skip
 
+# Flaky on buildbot. Issue 5133 and 10409.
+cc/Sleep: Pass, Fail
+
 [ $arch == x64 ]
 cc/IsolateInterrupt: Skip
 
-[ $system == windows && $mode == debug ]
-cc/Sleep: Pass, Fail  # Flaky on buildbot. Issue 5133.
-
 # The following section refers to the dart vm tests which live under
 # runtime/tests/vm/dart.
 [ $system == windows ]
 cc/Dart2JSCompileAll: Skip
 cc/ExternalizeConstantStrings: Skip
 
 [ $runtime == drt ]
 dart/isolate_mirror_local_test: Skip
 
 [ $compiler == dart2js || $compiler == dartc ]
@@ skipping 43 matching lines @@
 cc/Dart2JSCompileAll: Skip
 dart/byte_array_test: Skip
 dart/byte_array_optimized_test: Skip
 dart/inline_stack_frame_test: Skip
 
 # TODO(ajohnsen): Fix this as part of library changes.
 [ $compiler == none ]
 cc/CustomIsolates: Skip # Bug 6890
 cc/NewNativePort: Skip # Bug 6890
 cc/RunLoop_ExceptionParent: Skip # Bug 6890