Relanding precompiled header support for VS 2008, now enabled for

base/time_win.cc

Index: base/time_win.cc
diff --git a/base/time_win.cc b/base/time_win.cc
index 9bb04de7a47d19e1eabffd7343d2e90b6cba5405..9e6fe537741bf09cd71e89100b6571999da648da 100644
--- a/base/time_win.cc
+++ b/base/time_win.cc
@@ -363,7 +363,12 @@ class HighResNowSingleton {
     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: