Use a direct include of strings headers in chrome/browser/i*/.

chrome/browser/importer/nss_decryptor_null.h

 // 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.
 
 #ifndef CHROME_BROWSER_IMPORTER_NSS_DECRYPTOR_NULL_H_
 #define CHROME_BROWSER_IMPORTER_NSS_DECRYPTOR_NULL_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 namespace base {
 class FilePath;
 }
 
 namespace content {
 struct PasswordForm;
 }
 
 // A NULL wrapper for Firefox NSS decrypt component, for use in builds where
 // we do not have the NSS library.
 class NSSDecryptor {
  public:
   NSSDecryptor() {}
   bool Init(const base::FilePath& dll_path, const base::FilePath& db_path) { return false; }
   string16 Decrypt(const std::string& crypt) const { return string16(); }
   void ParseSignons(const std::string& content,
                     std::vector<content::PasswordForm>* forms) {}
   bool ReadAndParseSignons(const base::FilePath& sqlite_file,
                            std::vector<content::PasswordForm>* forms) {
     return false;
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NSSDecryptor);
 };
 
 #endif  // CHROME_BROWSER_IMPORTER_NSS_DECRYPTOR_NULL_H_