Use a direct include of strings headers in chrome/browser/r*-s*/.

chrome/browser/spellchecker/spellcheck_platform_mac.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.
 
 // This file defines the interface that any platform-specific spellchecker
 // needs to implement in order to be used by the browser.
 
 #ifndef CHROME_BROWSER_SPELLCHECKER_SPELLCHECK_PLATFORM_MAC_H_
 #define CHROME_BROWSER_SPELLCHECKER_SPELLCHECK_PLATFORM_MAC_H_
 
 #include <string>
 #include <vector>
 
 #include "base/callback_forward.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 struct SpellCheckResult;
 
 namespace content {
 class BrowserMessageFilter;
 }  // namespace content
 
 namespace spellcheck_mac {
 
 typedef base::Callback<void(
@@ skipping 77 matching lines @@
  public:
   ScopedEnglishLanguageForTest();
   ~ScopedEnglishLanguageForTest();
  private:
   SpellcheckerStateInternal* state_;
 };
 
 }  // namespace spellcheck_mac
 
 #endif  // CHROME_BROWSER_SPELLCHECKER_SPELLCHECK_PLATFORM_MAC_H_