iwyu: Cleanup in the following files:

base/base_paths_linux.cc

Index: base/base_paths_linux.cc
diff --git a/base/base_paths_linux.cc b/base/base_paths_linux.cc
index c32bc1934e8b81754bd166dee0f737ab53a2cf52..2ee690da881578db9a7259e39330db28f52b54ac 100644
--- a/base/base_paths_linux.cc
+++ b/base/base_paths_linux.cc
@@ -4,21 +4,23 @@
 
 #include "base/base_paths.h"
 
-#include <unistd.h>
-#if defined(OS_FREEBSD)
-#include <sys/param.h>
-#include <sys/sysctl.h>
-#endif
+#include <ostream>
+#include <string>
 
+#include "build/build_config.h"
 #include "base/environment.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/path_service.h"
-#include "base/sys_string_conversions.h"
 #include "base/nix/xdg_util.h"
 
+#if defined(OS_FREEBSD)
+#include <sys/param.h>
+#include <sys/sysctl.h>
+#endif
+
 namespace base {
 
 #if defined(OS_LINUX)