Fix performance regressions due to lazy initialization.

src/platform-win32.cc

Index: src/platform-win32.cc
diff --git a/src/platform-win32.cc b/src/platform-win32.cc
index 12cd610a3420c834d98efeea59f41ed59ebdbf33..d042924315ef87cef992a1dfd3d97d8b655e0c55 100644
--- a/src/platform-win32.cc
+++ b/src/platform-win32.cc
@@ -204,8 +204,10 @@ void init_fast_##name##_function() {                     \
   fast_##name##_function = generator;                    \
 }                                                        \
 double fast_##name(double x) {                           \
-  CallOnce(&fast_##name##_init_once,                     \
-           &init_fast_##name##_function);                \
+  if (!fast_##name##_function ) {                        \
+    CallOnce(&fast_##name##_init_once,                   \
+             &init_fast_##name##_function);              \
+  }                                                      \
   return (*fast_##name##_function)(x);                   \
 }