FileManagerBrowserTestBase: C includes before C++ includes

Tbr: slangley
Bug: 841659
Change-Id: Ie9c79c80a3105ced7d97636ad8cb519e66d99244
Reviewed-on: https://chromium-review.googlesource.com/1055409Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557839}

chrome/browser/chromeos/file_manager/file_manager_browsertest_base.cc

@@ -4,8 +4,8 @@
 
 #include "chrome/browser/chromeos/file_manager/file_manager_browsertest_base.h"
 
-#include <memory>
 #include <stddef.h>
+#include <memory>
 
 #include "base/containers/circular_deque.h"
 #include "base/json/json_reader.h"