Fix include ordering

OS_WIN is defined in build/build_config.h so #if defined(OS_WIN) must
appear after that include.

Change-Id: I3699e4bafb337f485eee62c6b782df46c21e7791
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730894
Auto-Submit: Carlos Caballero <carlscab@google.com>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#683527}

ipc/ipc_perftest_util.h

@@ -26,6 +26,10 @@
 #include "mojo/public/cpp/bindings/binding.h"
 #include "mojo/public/cpp/system/core.h"
 
+#if defined(OS_WIN)
+#include <windows.h>
+#endif
+
 namespace IPC {
 
 scoped_refptr<base::SingleThreadTaskRunner> GetIOThreadTaskRunner();