Use a direct include of strings headers in chrome/test/.

chrome/test/chromedriver/keycode_text_conversion.h

 // Copyright (c) 2013 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_TEST_CHROMEDRIVER_KEYCODE_TEXT_CONVERSION_H_
 #define CHROME_TEST_CHROMEDRIVER_KEYCODE_TEXT_CONVERSION_H_
 
 #include <string>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/base/keycodes/keyboard_codes.h"
 
 // These functions only support conversion of characters in the BMP
 // (Basic Multilingual Plane).
 
 // Returns the text in UTF8 that would be produced from the given key code and
 // modifiers with the current keyboard layout, or "" if no character would
 // be produced. This will return "" if the produced text contains characters
 // outside the BMP.
 std::string ConvertKeyCodeToText(ui::KeyboardCode key_code, int modifiers);
 
 // Converts a character to the key code and modifiers that would produce
 // the character using the current keyboard layout. Returns true on success.
 bool ConvertCharToKeyCode(
     char16 key, ui::KeyboardCode* key_code, int *necessary_modifiers);
 
 #endif  // CHROME_TEST_CHROMEDRIVER_KEYCODE_TEXT_CONVERSION_H_