Use a direct include of strings headers in base/.

base/base_paths_mac.mm

 // Copyright (c) 2012 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.
 
 // Defines base::PathProviderMac which replaces base::PathProviderPosix for Mac
 // in base/path_service.cc.
 
 #include <dlfcn.h>
 #import <Foundation/Foundation.h>
 #include <mach-o/dyld.h>
 
 #include "base/base_paths.h"
 #include "base/compiler_specific.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/path_service.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "build/build_config.h"
 
 namespace {
 
 void GetNSExecutablePath(base::FilePath* path) {
   DCHECK(path);
   // Executable path can have relative references ("..") depending on
   // how the app was launched.
   uint32_t executable_length = 0;
   _NSGetExecutablePath(NULL, &executable_length);
@@ skipping 73 matching lines @@
       return base::mac::GetUserDirectory(NSCachesDirectory, result);
     case base::DIR_HOME:
       *result = base::mac::NSStringToFilePath(NSHomeDirectory());
       return true;
     default:
       return false;
   }
 }
 
 }  // namespace base