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

mojo/edk/system/test/sleep_unittest.cc

-// Copyright 2015 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.
-
-#include "mojo/edk/system/test/sleep.h"
-
-#include "mojo/edk/system/test/stopwatch.h"
-#include "mojo/edk/system/test/timeouts.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace mojo {
-namespace system {
-namespace test {
-namespace {
-
-TEST(SleepTest, Sleep) {
-  Stopwatch stopwatch;
-
-  stopwatch.Start();
-  Sleep(0ULL);
-  EXPECT_LT(stopwatch.Elapsed(), EpsilonTimeout());
-
-  stopwatch.Start();
-  Sleep(2 * EpsilonTimeout());
-  MojoDeadline elapsed = stopwatch.Elapsed();
-  EXPECT_GT(elapsed, EpsilonTimeout());
-  EXPECT_LT(elapsed, 3 * EpsilonTimeout());
-}
-
-TEST(SleepTest, SleepMilliseconds) {
-  Stopwatch stopwatch;
-
-  stopwatch.Start();
-  SleepMilliseconds(0U);
-  EXPECT_LT(stopwatch.Elapsed(), EpsilonTimeout());
-
-  const MojoDeadline kMillisecondsPerMicrosecond = 1000ULL;
-  unsigned epsilon_ms =
-      static_cast<unsigned>(EpsilonTimeout() / kMillisecondsPerMicrosecond);
-  stopwatch.Start();
-  SleepMilliseconds(2 * epsilon_ms);
-  MojoDeadline elapsed = stopwatch.Elapsed();
-  EXPECT_GT(elapsed, EpsilonTimeout());
-  EXPECT_LT(elapsed, 3 * EpsilonTimeout());
-}
-
-}  // namespace
-}  // namespace test
-}  // namespace system
-}  // namespace mojo