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

mojo/edk/platform/thread_utils_unittest.cc

+// Copyright 2016 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/platform/thread_utils.h"
+
+#include "mojo/edk/system/test/stopwatch.h"
+#include "mojo/edk/system/test/timeouts.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using mojo::system::test::EpsilonTimeout;
+using mojo::system::test::Stopwatch;
+
+namespace mojo {
+namespace platform {
+namespace {
+
+TEST(ThreadUtils, ThreadYield) {
+  // It's pretty hard to test yield, other than maybe statistically (but tough
+  // even then, since it'd be dependent on the number of cores). So just check
+  // that it doesn't crash.
+  ThreadYield();
+}
+
+TEST(ThreadUtils, ThreadSleep) {
+  Stopwatch stopwatch;
+
+  stopwatch.Start();
+  ThreadSleep(0ULL);
+  EXPECT_LT(stopwatch.Elapsed(), EpsilonTimeout());
+
+  stopwatch.Start();
+  ThreadSleep(2 * EpsilonTimeout());
+  MojoDeadline elapsed = stopwatch.Elapsed();
+  EXPECT_GT(elapsed, EpsilonTimeout());
+  EXPECT_LT(elapsed, 3 * EpsilonTimeout());
+}
+
+}  // namespace
+}  // namespace platform
+}  // namespace mojo