Remove support for custom NSURLProtocol.

ios/chrome/app/startup/network_stack_setup.mm

 // Copyright 2016 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/chrome/app/startup/network_stack_setup.h"
 
 #include "base/memory/ptr_util.h"
 #include "ios/chrome/browser/application_context.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
 #import "ios/net/empty_nsurlcache.h"
 #include "ios/web/net/request_tracker_factory_impl.h"
-#include "ios/web/net/web_http_protocol_handler_delegate.h"
 
 @implementation NetworkStackSetup
 
-+ (void)setUpChromeNetworkStack:
-            (std::unique_ptr<web::RequestTrackerFactoryImpl>*)
-                requestTrackerFactory
-    httpProtocolHandlerDelegate:
-        (std::unique_ptr<web::WebHTTPProtocolHandlerDelegate>*)
-            httpProtocolHandlerDelegate {
++ (std::unique_ptr<web::RequestTrackerFactoryImpl>)setUpChromeNetworkStack {
   // Disable the default cache.
   [NSURLCache setSharedURLCache:[EmptyNSURLCache emptyNSURLCache]];
 
-  // Configuration for the HTTP protocol handler.
-  //  TODO(crbug.com/585700): Remove this code.
-  *httpProtocolHandlerDelegate =
-      base::MakeUnique<web::WebHTTPProtocolHandlerDelegate>(
-          GetApplicationContext()->GetSystemURLRequestContext());
-  net::HTTPProtocolHandlerDelegate::SetInstance(
-      httpProtocolHandlerDelegate->get());
-
-  // Register the chrome http protocol handler to replace the default one.
-  // TODO(crbug.com/665036): Move the network stack initialization to the web
-  // layer.
-  BOOL success = [NSURLProtocol registerClass:[CRNHTTPProtocolHandler class]];
-  DCHECK(success);
-  *requestTrackerFactory =
+  auto requestTrackerFactory =
       base::MakeUnique<web::RequestTrackerFactoryImpl>(kChromeUIScheme);
-  net::RequestTracker::SetRequestTrackerFactory(requestTrackerFactory->get());
-
-  DCHECK(success);
+  net::RequestTracker::SetRequestTrackerFactory(requestTrackerFactory.get());
+  return requestTrackerFactory;
 }
 
 @end