Relanding precompiled header support for VS 2008, now enabled for

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 345 matching lines @@
       return TimeDelta::FromMicroseconds(UnreliableNow());
 
     // Just fallback to the slower clock.
     return RolloverProtectedNow();
   }
 
   int64 GetQPCDriftMicroseconds() {
     if (!IsUsingHighResClock())
       return 0;
 
-    return abs((UnreliableNow() - ReliableNow()) - skew_);
+    // The static_cast<long> is needed as a hint to VS 2008 to tell it
+    // which version of abs() to use. Other compilers don't seem to
+    // need it, including VS 2010, but to keep code identical we use it
+    // everywhere.
+    // TODO(joi): Remove the hint if/when we no longer support VS 2008.
+    return abs(static_cast<long>((UnreliableNow() - ReliableNow()) - skew_));
   }
 
  private:
   HighResNowSingleton()
     : ticks_per_microsecond_(0.0),
       skew_(0) {
     InitializeClock();
 
     // On Athlon X2 CPUs (e.g. model 15) QueryPerformanceCounter is
     // unreliable.  Fallback to low-res clock.
@@ skipping 55 matching lines @@
 
 // static
 int64 TimeTicks::GetQPCDriftMicroseconds() {
   return HighResNowSingleton::GetInstance()->GetQPCDriftMicroseconds();
 }
 
 // static
 bool TimeTicks::IsHighResClockWorking() {
   return HighResNowSingleton::GetInstance()->IsUsingHighResClock();
 }