Fix clang/win build after https://codereview.chromium.org/1284053004/

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 362 matching lines @@
 // (3) System time. The system time provides a low-resolution (from ~1 to ~15.6
 // milliseconds) time stamp but is comparatively less expensive to retrieve and
 // more reliable. Time::EnableHighResolutionTimer() and
 // Time::ActivateHighResolutionTimer() can be called to alter the resolution of
 // this timer; and also other Windows applications can alter it, affecting this
 // one.
 
 using NowFunction = TimeDelta (*)(void);
 
 TimeDelta InitialNowFunction();
-TimeDelta InitialSystemTraceNowFunction();
 
 // See "threading notes" in InitializeNowFunctionPointer() for details on how
 // concurrent reads/writes to these globals has been made safe.
 NowFunction g_now_function = &InitialNowFunction;
 int64 g_qpc_ticks_per_second = 0;
 
 // As of January 2015, use of <atomic> is forbidden in Chromium code. This is
 // what std::atomic_thread_fence does on Windows on all Intel architectures when
 // the memory_order argument is anything but std::memory_order_seq_cst:
 #define ATOMIC_THREAD_FENCE(memory_order) _ReadWriteBarrier();
@@ skipping 124 matching lines @@
 TimeTicks TimeTicks::FromQPCValue(LONGLONG qpc_value) {
   return TimeTicks() + QPCValueToTimeDelta(qpc_value);
 }
 
 // TimeDelta ------------------------------------------------------------------
 
 // static
 TimeDelta TimeDelta::FromQPCValue(LONGLONG qpc_value) {
   return QPCValueToTimeDelta(qpc_value);
 }