Make the request initiator Optional

content/browser/loader/resource_dispatcher_host_impl.cc

 // Copyright (c) 2012 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.
 
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
 
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 
 #include <stddef.h>
 
@@ skipping 1389 matching lines @@
   // stream that contains the response body of a navigation. Otherwise the data
   // that was already fetched by the browser will not be transmitted to the
   // renderer.
   if (is_navigation_stream_request)
     new_request->set_method("GET");
   else
     new_request->set_method(request_data.method);
 
   new_request->set_first_party_for_cookies(
       request_data.first_party_for_cookies);
+
+  // The initiator should normally be present, unless this is a navigation in a
+  // top-level frame. It may be null for some top-level navigations (eg:
+  // browser-initiated ones).
+  DCHECK(request_data.request_initiator.has_value() ||
+         request_data.resource_type == RESOURCE_TYPE_MAIN_FRAME);
   new_request->set_initiator(request_data.request_initiator);
 
   if (request_data.originated_from_service_worker) {
     new_request->SetUserData(URLRequestServiceWorkerData::kUserDataKey,
                              new URLRequestServiceWorkerData());
   }
 
   // If the request is a MAIN_FRAME request, the first-party URL gets updated on
   // redirects.
   if (request_data.resource_type == RESOURCE_TYPE_MAIN_FRAME) {
@@ skipping 1365 matching lines @@
                                  &throttles);
     if (!throttles.empty()) {
       handler.reset(new ThrottlingResourceHandler(std::move(handler), request,
                                                   std::move(throttles)));
     }
   }
   return handler;
 }
 
 }  // namespace content