Add interface to system trace clock.

base/time_win.cc

 // Copyright (c) 2011 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.
 
 
 // Windows Timer Primer
 //
 // A good article:  http://www.ddj.com/windows/184416651
 // A good mozilla bug:  http://bugzilla.mozilla.org/show_bug.cgi?id=363258
 //
@@ skipping 418 matching lines @@
 TimeTicks TimeTicks::Now() {
   return TimeTicks() + RolloverProtectedNow();
 }
 
 // static
 TimeTicks TimeTicks::HighResNow() {
   return TimeTicks() + HighResNowSingleton::GetInstance()->Now();
 }
 
 // static
+TimeTicks TimeTicks::NowFromSystemTraceTime() {
+  return HighResNow();
+}
+
+// static
 int64 TimeTicks::GetQPCDriftMicroseconds() {
   return HighResNowSingleton::GetInstance()->GetQPCDriftMicroseconds();
 }
 
 // static
 bool TimeTicks::IsHighResClockWorking() {
   return HighResNowSingleton::GetInstance()->IsUsingHighResClock();
 }