Add UMA for High Resolution Timer Usage

base/time/time_win_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 <windows.h>
 #include <mmsystem.h>
 #include <process.h>
 #include <stdint.h>
 
 #include <cmath>
@@ skipping 282 matching lines @@
         << "ticks=" << ticks << ", to be converted via logic path: "
         << (ticks < Time::kQPCOverflowThreshold ? "FAST" : "SAFE");
   }
 }
 
 TEST(TimeDelta, ConstexprInitialization) {
   // Make sure that TimeDelta works around crbug.com/635974
   EXPECT_EQ(kExpectedDeltaInMilliseconds, kConstexprTimeDelta.InMilliseconds());
 }
 
+TEST(HighResolutionTimer, GetUsage) {
+  EXPECT_EQ(0.0, Time::GetHighResolutionTimerUsage());
+
+  Time::ResetHighResolutionTimerUsage();
+
+  // 0% usage since the timer isn't activated regardless of how much time has
+  // elapsed.
+  EXPECT_EQ(0.0, Time::GetHighResolutionTimerUsage());
+  Sleep(10);
+  EXPECT_EQ(0.0, Time::GetHighResolutionTimerUsage());
+
+  Time::ActivateHighResolutionTimer(true);
+  Time::ResetHighResolutionTimerUsage();
+
+  Sleep(20);
+  // 100% usage since the timer has been activated entire time.
+  EXPECT_EQ(100.0, Time::GetHighResolutionTimerUsage());
+
+  Time::ActivateHighResolutionTimer(false);
+  Sleep(20);
+  double usage1 = Time::GetHighResolutionTimerUsage();
+  // usage1 should be about 50%.
+  EXPECT_LT(usage1, 100.0);
+  EXPECT_GT(usage1, 0.0);
+
+  Time::ActivateHighResolutionTimer(true);
+  Sleep(10);
+  Time::ActivateHighResolutionTimer(false);
+  double usage2 = Time::GetHighResolutionTimerUsage();
+  // usage2 should be about 60%.
+  EXPECT_LT(usage2, 100.0);
+  EXPECT_GT(usage2, usage1);
+
+  Time::ResetHighResolutionTimerUsage();
+  EXPECT_EQ(0.0, Time::GetHighResolutionTimerUsage());
+}
+
 }  // namespace base