Revert "EDK: Move //mojo/edk/system/waitable_event* to edk/util."

mojo/edk/util/mutex_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/util/mutex.h"
 
 #include <stdlib.h>
 
 #include <thread>
 
 #include "mojo/edk/system/test/sleep.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-using mojo::system::test::SleepMilliseconds;
-
 namespace mojo {
 namespace util {
 namespace {
 
 // Sleeps for a "very small" amount of time.
 void EpsilonRandomSleep() {
-  SleepMilliseconds(static_cast<unsigned>(rand()) % 20u);
+  system::test::SleepMilliseconds(static_cast<unsigned>(rand()) % 20u);
 }
 
 // Basic test to make sure that Lock()/Unlock()/TryLock() don't crash ----------
 
 TEST(MutexTest, Basic) {
   Mutex mutex;
 
   int thread_acquired = 0;
   auto thread = std::thread([&mutex, &thread_acquired]() {
     for (int i = 0; i < 10; i++) {
@@ skipping 161 matching lines @@
 
   // The destruction of |locker| should unlock |mutex|.
   ASSERT_TRUE(mutex.TryLock());
   mutex.AssertHeld();
   mutex.Unlock();
 }
 
 }  // namespace
 }  // namespace util
 }  // namespace mojo