Fix performance regressions due to lazy initialization.

src/platform-macos.cc

Index: src/platform-macos.cc
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index bfcaab0b51f13f7f1ce9ad1410c855c724a5f4db..dbcd80e9f21222faab02df1aab68f3958f7b27f4 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -58,6 +58,7 @@
 
 #include "v8.h"
 
+#include "platform-posix.h"
 #include "platform.h"
 #include "vm-state-inl.h"
 
@@ -101,6 +102,13 @@ void OS::SetUp() {
 }
 
 
+void OS::PostSetUp() {
+  // Math functions depend on CPU features therefore they are initialized after
+  // CPU.
+  MathSetup();
+}
+
+
 // We keep the lowest and highest addresses mapped as a quick way of
 // determining that pointers are outside the heap (used mostly in assertions
 // and verification).  The estimate is conservative, i.e., not all addresses in