Divide CookieStoreIOS into two different classes with different backends

ios/crnet/crnet_environment.mm

 // Copyright 2014 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 "ios/crnet/crnet_environment.h"
 
 #import <Foundation/Foundation.h>
 
 #include <utility>
 
@@ skipping 459 matching lines @@
   // TODO(mmenke):  These really shouldn't be leaked.
   //                See https://crbug.com/523858.
   net::HttpNetworkSession* http_network_session =
       new net::HttpNetworkSession(params);
   net::HttpCache* main_cache =
       new net::HttpCache(http_network_session, std::move(main_backend),
                          true /* set_up_quic_server_info */);
   main_context_->set_http_transaction_factory(main_cache);
 
   // Cookies
-  cookie_store_ = net::CookieStoreIOS::CreateCookieStore(
+  cookie_store_ = base::MakeUnique<CookieStoreIOS>(
       [NSHTTPCookieStorage sharedHTTPCookieStorage]);
   main_context_->set_cookie_store(cookie_store_.get());
 
   net::URLRequestJobFactoryImpl* job_factory =
       new net::URLRequestJobFactoryImpl;
   job_factory->SetProtocolHandler(
       "data", base::WrapUnique(new net::DataProtocolHandler));
 #if !BUILDFLAG(DISABLE_FILE_SUPPORT)
   job_factory->SetProtocolHandler(
       "file",
@@ skipping 13 matching lines @@
 
   return user_agent_settings->GetUserAgent();
 }
 
 void CrNetEnvironment::ClearCache(ClearCacheCallback callback) {
   PostToNetworkThread(
       FROM_HERE, base::Bind(&net::ClearHttpCache, main_context_getter_,
                             network_io_thread_->task_runner(), base::Time(),
                             base::Time::Max(), base::BindBlock(callback)));
 }