Change chrome from statically enabling high resolution timers on windows...

base/time.h

 // Copyright (c) 2010 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 time, internally represented as
 // microseconds (s/1,000,000) since a platform-dependent epoch.  Each
 // platform's epoch, along with other system-dependent clock interface
 // routines, is defined in time_PLATFORM.cc.
 //
 // TimeDelta represents a duration of time, internally represented in
@@ skipping 236 matching lines @@
   double ToDoubleT() const;
 
 #if defined(OS_POSIX)
   struct timeval ToTimeVal() const;
 #endif
 
 #if defined(OS_WIN)
   static Time FromFileTime(FILETIME ft);
   FILETIME ToFileTime() const;
 
-  // Enable or disable Windows high resolution timer. For more details
-  // see comments in time_win.cc. Returns true on success.
-  static bool UseHighResolutionTimer(bool use);
+  // The minimum time of a low resolution timer.  This is basically a windows
+  // constant of ~15.6ms.  While it does vary on some older OS versions, we'll
+  // treat it as static across all windows versions.
+  static const int kMinLowResolutionThresholdMs = 16;
+
+  // Enable or disable Windows high resolution timer. If the high resolution
+  // timer is not enabled, calls to ActivateHighResolutionTimer will fail.
+  // When disabling the high resolution timer, this function will not cause
+  // the high resolution timer to be deactivated, but will prevent future
+  // activations.
+  // Must be called from the main thread.
+  // For more details see comments in time_win.cc.
+  static void EnableHighResolutionTimer(bool enable);
+
+  // Activates or deactivates the high resolution timer based on the |activate|
+  // flag.  If the HighResolutionTimer is not Enabled (see
+  // EnableHighResolutionTimer), this function will return false.  Otherwise
+  // returns true.
+  // All callers to activate the high resolution timer must eventually call
+  // this function to deactivate the high resolution timer.
+  static bool ActivateHighResolutionTimer(bool activate);
 #endif
 
   // Converts an exploded structure representing either the local time or UTC
   // into a Time class.
   static Time FromUTCExploded(const Exploded& exploded) {
     return FromExploded(false, exploded);
   }
   static Time FromLocalExploded(const Exploded& exploded) {
     return FromExploded(true, exploded);
   }
@@ skipping 93 matching lines @@
   // |is_local = true| or UTC |is_local = false|.
   static Time FromExploded(bool is_local, const Exploded& exploded);
 
   explicit Time(int64 us) : us_(us) {
   }
 
   // The representation of Jan 1, 1970 UTC in microseconds since the
   // platform-dependent epoch.
   static const int64 kTimeTToMicrosecondsOffset;
 
+#if defined(OS_WIN)
+  // Indicates whether fast timers are usable right now.  For instance,
+  // when using battery power, we might elect to prevent high speed timers
+  // which would draw more power.
+  static bool high_resolution_timer_enabled_;
+#endif
+
   // Time in microseconds in UTC.
   int64 us_;
 };
 
 inline Time TimeDelta::operator+(Time t) const {
   return Time(t.us_ + delta_);
 }
 
 // Inline the TimeDelta factory methods, for fast TimeDelta construction.
 
@@ skipping 121 matching lines @@
 #endif
 };
 
 inline TimeTicks TimeDelta::operator+(TimeTicks t) const {
   return TimeTicks(t.ticks_ + delta_);
 }
 
 }  // namespace base
 
 #endif  // BASE_TIME_H_