Make SystemMonitor not a Singleton and move it out of base

base/time.h

 // Copyright (c) 2009 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 224 matching lines @@
   // Converts time to/from a double which is the number of seconds since epoch
   // (Jan 1, 1970).  Webkit uses this format to represent time.
   static Time FromDoubleT(double dt);
   double ToDoubleT() const;
 
 
 #if defined(OS_WIN)
   static Time FromFileTime(FILETIME ft);
   FILETIME ToFileTime() const;
 
-  // Monitor system power state and disable high resolution timer when we're
-  // on battery. See time_win.cc for more details.
-  static void StartSystemMonitorObserver();
-
-  // Enable high resolution timer unconditionally. Only for test code.
-  static void EnableHiResClockForTests();
+  // 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);
 #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 234 matching lines @@
 #endif
 };
 
 inline TimeTicks TimeDelta::operator+(TimeTicks t) const {
   return TimeTicks(t.ticks_ + delta_);
 }
 
 }  // namespace base
 
 #endif  // BASE_TIME_H_