Remove some unused linked_ptr.h includes in c/b/extensions/api

chrome/browser/extensions/api/language_settings_private/language_settings_private_delegate.cc

 // Copyright 2015 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/browser/extensions/api/language_settings_private/language_settings_private_delegate.h"
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
-#include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/spellchecker/spellcheck_factory.h"
 #include "chrome/browser/spellchecker/spellcheck_service.h"
 #include "components/prefs/pref_service.h"
 #include "components/spellcheck/browser/pref_names.h"
 #include "content/public/browser/browser_context.h"
@@ skipping 225 matching lines @@
 }
 
 void LanguageSettingsPrivateDelegate::RemoveDictionaryObservers() {
   for (const auto& dictionary : hunspell_dictionaries_) {
     if (dictionary)
       dictionary->RemoveObserver(this);
   }
 }
 
 }  // namespace extensions