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

chrome/browser/extensions/api/developer_private/developer_private_mangle.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_MANGLE_H_
 #define CHROME_BROWSER_EXTENSIONS_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_MANGLE_H_
 
-#include "base/memory/linked_ptr.h"
-
 namespace extensions {
 
 namespace api {
 namespace developer_private {
 struct ItemInfo;
 struct ExtensionInfo;
 }
 }
 
 namespace developer_private_mangle {
 
 // Converts a developer_private::ExtensionInfo into a
 // developer_private::ItemInfo for compatability with deprecated API
 // functions.
 api::developer_private::ItemInfo MangleExtensionInfo(
     const api::developer_private::ExtensionInfo& info);
 
 }  // namespace developer_private_mangle
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_MANGLE_H_