Add HttpProtocolHandler and convert everything to use it

ios/chrome/browser/ios_chrome_io_thread.mm

Index: ios/chrome/browser/ios_chrome_io_thread.mm
diff --git a/ios/chrome/browser/ios_chrome_io_thread.mm b/ios/chrome/browser/ios_chrome_io_thread.mm
index 763c0280813c3b0d6b298cc44c1a14e00c452339..6c2a67fc124542f94bca61f41cda5181290885ae 100644
--- a/ios/chrome/browser/ios_chrome_io_thread.mm
+++ b/ios/chrome/browser/ios_chrome_io_thread.mm
@@ -1017,14 +1017,14 @@ net::URLRequestContext* IOSChromeIOThread::ConstructSystemRequestContext(
       globals->http_auth_handler_factory.get());
   context->set_proxy_service(globals->system_proxy_service.get());
 
-  net::URLRequestJobFactoryImpl* system_job_factory =
-      new net::URLRequestJobFactoryImpl();
+  std::unique_ptr<net::URLRequestJobFactoryImpl> system_job_factory =
+      net::URLRequestJobFactoryImpl::CreateWithDefaultProtocolHandlers();
   // Data URLs are always loaded through the system request context on iOS
   // (due to UIWebView limitations).
   bool set_protocol = system_job_factory->SetProtocolHandler(
       url::kDataScheme, base::WrapUnique(new net::DataProtocolHandler()));
   DCHECK(set_protocol);
-  globals->system_url_request_job_factory.reset(system_job_factory);
+  globals->system_url_request_job_factory = std::move(system_job_factory);
   context->set_job_factory(globals->system_url_request_job_factory.get());
 
   context->set_cookie_store(globals->system_cookie_store.get());