Improve the fix for r18344.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index 1076be0271142cf60f878b332125df4baa5f4286..4ac2fb49eafc41429f4deaf91d16573126c296cb 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -1388,15 +1388,11 @@ ExternalReference ExternalReference::address_of_regexp_stack_memory_size(
 #endif  // V8_INTERPRETED_REGEXP
 
 
-static double math_log_double(double x) {
-  return log(x);
-}
-
-
 ExternalReference ExternalReference::math_log_double_function(
     Isolate* isolate) {
+  typedef double (*d2d)(double x);
   return ExternalReference(Redirect(isolate,
-                                    FUNCTION_ADDR(math_log_double),
+                                    FUNCTION_ADDR(static_cast<d2d>(log)),
                                     BUILTIN_FP_CALL));
 }