Add //mojo/edk/platform/thread_utils.* containing "yield" and "sleep".

mojo/edk/system/test/sleep.h

Index: mojo/edk/system/test/sleep.h
diff --git a/mojo/edk/system/test/sleep.h b/mojo/edk/system/test/sleep.h
deleted file mode 100644
index ff8e4f08da6ac4900e357e161dcd2e8367360bff..0000000000000000000000000000000000000000
--- a/mojo/edk/system/test/sleep.h
+++ /dev/null
@@ -1,24 +0,0 @@
-// Copyright 2013 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Function for sleeping in tests. (Please use sparingly.)
-
-#ifndef MOJO_EDK_SYSTEM_TEST_SLEEP_H_
-#define MOJO_EDK_SYSTEM_TEST_SLEEP_H_
-
-#include "mojo/public/c/system/types.h"
-
-namespace mojo {
-namespace system {
-namespace test {
-
-// Sleeps for at least the specified duration.
-void Sleep(MojoDeadline duration);
-void SleepMilliseconds(unsigned duration_milliseconds);
-
-}  // namespace test
-}  // namespace system
-}  // namespace mojo
-
-#endif  // MOJO_EDK_SYSTEM_TEST_SLEEP_H_