Use a direct include of strings headers in chrome_frame/.

chrome_frame/registry_list_preferences_holder.h

 // 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.
 
 // A utility class for accessing and caching registry preferences that take
 // the form of lists of strings.
 // TODO(robertshield): Use the RegistryWatcher stuff to keep this list up to
 // date.
 
 #ifndef CHROME_FRAME_REGISTRY_LIST_PREFERENCES_HOLDER_H_
 #define CHROME_FRAME_REGISTRY_LIST_PREFERENCES_HOLDER_H_
 
 #include <windows.h>
 
 #include <vector>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 class RegistryListPreferencesHolder {
  public:
   RegistryListPreferencesHolder();
 
   // Initializes the RegistryListPreferencesHolder using the values stored
   // under the key |list_name| stored at |registry_path| under |hive|.
   void Init(HKEY hive,
             const wchar_t* registry_path,
             const wchar_t* list_name);
@@ skipping 13 matching lines @@
   void ResetForTesting();
 
  private:
   std::vector<string16> values_;
   bool valid_;
 
   DISALLOW_COPY_AND_ASSIGN(RegistryListPreferencesHolder);
 };
 
 #endif  // CHROME_FRAME_REGISTRY_LIST_PREFERENCES_HOLDER_H_