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

chrome/test/webdriver/webdriver_key_converter.cc

 // 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.
 
 #include "chrome/test/webdriver/webdriver_key_converter.h"
 
 #include "base/format_macros.h"
 #include "base/logging.h"
-#include "base/stringprintf.h"
+#include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/common/automation_constants.h"
 #include "chrome/test/automation/automation_json_requests.h"
 #include "chrome/test/webdriver/keycode_text_conversion.h"
 #include "chrome/test/webdriver/webdriver_logging.h"
 
 namespace {
 
 struct ModifierMaskAndKeyCode {
   int mask;
@@ skipping 306 matching lines @@
             CreateKeyUpEvent(kModifiers[i].key_code, sticky_modifiers));
       }
     }
   }
   client_key_events->swap(key_events);
   *modifiers = sticky_modifiers;
   return true;
 }
 
 }  // namespace webdriver