Use a direct include of strings headers in base/.

base/native_library_mac.mm

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/native_library.h"
 
 #include <dlfcn.h>
 #include <mach-o/getsect.h>
 
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/mac/scoped_cftyperef.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
 
 namespace base {
 
 static NativeLibraryObjCStatus GetObjCStatusForImage(
     const void* function_pointer) {
   Dl_info info;
   if (!dladdr(function_pointer, &info))
     return OBJC_UNKNOWN;
@@ skipping 94 matching lines @@
 
   return function_pointer;
 }
 
 // static
 string16 GetNativeLibraryName(const string16& name) {
   return name + ASCIIToUTF16(".dylib");
 }
 
 }  // namespace base