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

chrome/browser/extensions/api/signed_in_devices/signed_in_devices_manager.cc

 // Copyright 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.
 
 #include "chrome/browser/extensions/api/signed_in_devices/signed_in_devices_manager.h"
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/lazy_instance.h"
-#include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/api/signed_in_devices/signed_in_devices_api.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sync/profile_sync_service_factory.h"
 #include "chrome/common/extensions/api/signed_in_devices.h"
 #include "components/browser_sync/browser/profile_sync_service.h"
 #include "components/sync/device_info/device_info.h"
 #include "extensions/browser/event_router.h"
@@ skipping 133 matching lines @@
 }
 
 void SignedInDevicesManager::OnExtensionUnloaded(
     content::BrowserContext* browser_context,
     const Extension* extension,
     UnloadedExtensionInfo::Reason reason) {
   RemoveChangeObserverForExtension(extension->id());
 }
 
 }  // namespace extensions