Kills TraceTicks, which was functionally the same as TimeTicks

base/time/time_win.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.
 
 
 // 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 30 matching lines @@
 #include "base/basictypes.h"
 #include "base/cpu.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/synchronization/lock.h"
 
 using base::ThreadTicks;
 using base::Time;
 using base::TimeDelta;
 using base::TimeTicks;
-using base::TraceTicks;
 
 namespace {
 
 // From MSDN, FILETIME "Contains a 64-bit value representing the number of
 // 100-nanosecond intervals since January 1, 1601 (UTC)."
 int64 FileTimeToMicroseconds(const FILETIME& ft) {
   // Need to bit_cast to fix alignment, then divide by 10 to convert
   // 100-nanoseconds to microseconds. This only works on little-endian
   // machines.
   return bit_cast<int64, FILETIME>(ft) / 10;
@@ skipping 390 matching lines @@
   // the low-resolution clock.
   //
   // If the QPC implementation is expensive and/or unreliable, TimeTicks::Now()
   // will still use the low-resolution clock. A CPU lacking a non-stop time
   // counter will cause Windows to provide an alternate QPC implementation that
   // works, but is expensive to use. Certain Athlon CPUs are known to make the
   // QPC implementation unreliable.
   //
   // Otherwise, Now uses the high-resolution QPC clock. As of 21 August 2015,
   // ~72% of users fall within this category.
-  //
-  // TraceTicks::Now() always uses the same clock as TimeTicks::Now(), even
-  // when the QPC exists but is expensive or unreliable. This is because we'd
-  // eventually like to merge TraceTicks and TimeTicks and have one type of
-  // timestamp that is reliable, monotonic, and comparable. Also, while we could
-  // use the high-resolution timer for TraceTicks even when it's unreliable or
-  // slow, it's easier to make tracing tools accommodate a coarse timer than
-  // one that's unreliable or slow.
   NowFunction now_function;
   base::CPU cpu;
   if (ticks_per_sec.QuadPart <= 0 ||
       !cpu.has_non_stop_time_stamp_counter() || IsBuggyAthlon(cpu)) {
     now_function = &RolloverProtectedNow;
   } else {
     now_function = &QPCNow;
   }
 
   // Threading note 1: In an unlikely race condition, it's possible for two or
@@ skipping 126 matching lines @@
 
   // Compute the frequency of the TSC.
   DCHECK_GE(tsc_now, tsc_initial);
   uint64 tsc_ticks = tsc_now - tsc_initial;
   tsc_ticks_per_second = tsc_ticks / elapsed_time_seconds;
 
   return tsc_ticks_per_second;
 }
 
 // static
-TraceTicks TraceTicks::Now() {
-  return TraceTicks() + g_now_function();
-}
-
-// static
 TimeTicks TimeTicks::FromQPCValue(LONGLONG qpc_value) {
   return TimeTicks() + QPCValueToTimeDelta(qpc_value);
 }
 
 // TimeDelta ------------------------------------------------------------------
 
 // static
 TimeDelta TimeDelta::FromQPCValue(LONGLONG qpc_value) {
   return QPCValueToTimeDelta(qpc_value);
 }