Add UMA for High Resolution Timer Usage

base/timer/hi_res_timer_manager_unittest.cc

 // Copyright (c) 2012 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 "base/timer/hi_res_timer_manager.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/message_loop/message_loop.h"
 #include "base/power_monitor/power_monitor.h"
 #include "base/power_monitor/power_monitor_device_source.h"
+#include "base/test/scoped_task_scheduler.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 #if defined(OS_WIN)
 TEST(HiResTimerManagerTest, ToggleOnOff) {
   // The power monitor creates Window to receive power notifications from
   // Windows, which makes this test flaky if you run while the machine
   // goes in or out of AC power.
   base::MessageLoop loop(base::MessageLoop::TYPE_UI);
+  // Needed for HighResolutionTimerManager.
+  base::test::ScopedTaskScheduler task_scheduler(&loop);

[gab, 2017/06/28 16:39:33]

ScopedTaskScheduler is deprecated. Please replace the MessageLoop with
base::test::ScopedTaskEnvironment instead.

[stanisc, 2017/06/28 22:28:35]

Done.

   std::unique_ptr<base::PowerMonitorSource> power_monitor_source(
       new base::PowerMonitorDeviceSource());
   std::unique_ptr<base::PowerMonitor> power_monitor(
       new base::PowerMonitor(std::move(power_monitor_source)));
 
   HighResolutionTimerManager manager;
   // Simulate a on-AC power event to get to a known initial state.
   manager.OnPowerStateChange(false);
 
   // Loop a few times to test power toggling.
@@ skipping 17 matching lines @@
     EXPECT_TRUE(manager.hi_res_clock_available());
     EXPECT_TRUE(base::Time::IsHighResolutionTimerInUse());
 
     // De-activate the high resolution timer.
     base::Time::ActivateHighResolutionTimer(false);
   }
 }
 #endif  // defined(OS_WIN)
 
 }  // namespace base