Add UMA for High Resolution Timer Usage

base/time/time.h

 // 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.
 
 // Time represents an absolute point in coordinated universal time (UTC),
 // internally represented as microseconds (s/1,000,000) since the Windows epoch
 // (1601-01-01 00:00:00 UTC). System-dependent clock interface routines are
 // defined in time_PLATFORM.cc. Note that values for Time may skew and jump
 // around as the operating system makes adjustments to synchronize (e.g., with
 // NTP servers). Thus, client code that uses the Time class must account for
@@ skipping 531 matching lines @@
   // returns true.  Each successful activate call must be paired with a
   // subsequent deactivate call.
   // All callers to activate the high resolution timer must eventually call
   // this function to deactivate the high resolution timer.
   static bool ActivateHighResolutionTimer(bool activate);
 
   // Returns true if the high resolution timer is both enabled and activated.
   // This is provided for testing only, and is not tracked in a thread-safe
   // way.
   static bool IsHighResolutionTimerInUse();
-#endif
+
+  // The following two functions are used to report the fraction of elapsed time
+  // that the high resolution timer is activated.
+  // ResetHighResolutionTimerUsage() resets the cumulative usage and starts the
+  // measurement interval and GetHighResolutionTimerUsage() returns the
+  // percentage of time since the reset that the high resolution timer was
+  // activated.
+  // ResetHighResolutionTimerUsage() must be called at least once before calling
+  // GetHighResolutionTimerUsage(); otherwise the usage result would be
+  // undefined.
+  static void ResetHighResolutionTimerUsage();
+  static double GetHighResolutionTimerUsage();
+#endif  // defined(OS_WIN)
 
   // Converts an exploded structure representing either the local time or UTC
   // into a Time class. Returns false on a failure when, for example, a day of
   // month is set to 31 on a 28-30 day month. Returns Time(0) on overflow.
   static bool FromUTCExploded(const Exploded& exploded,
                               Time* time) WARN_UNUSED_RESULT {
     return FromExploded(false, exploded, time);
   }
   static bool FromLocalExploded(const Exploded& exploded,
                                 Time* time) WARN_UNUSED_RESULT {
@@ skipping 308 matching lines @@
   static void WaitUntilInitializedWin();
 #endif
 };
 
 // For logging use only.
 BASE_EXPORT std::ostream& operator<<(std::ostream& os, ThreadTicks time_ticks);
 
 }  // namespace base
 
 #endif  // BASE_TIME_TIME_H_