Limit Link header based SW installations for fetches made by SW.

content/browser/service_worker/link_header_support.cc

 // 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 "content/browser/service_worker/link_header_support.h"
 
 #include "base/command_line.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "components/link_header_util/link_header_util.h"
@@ skipping 47 matching lines @@
              : service_worker_context_for_testing;
   if (IsBrowserSideNavigationEnabled() &&
       ServiceWorkerUtils::IsMainResourceType(request_info->GetResourceType()) &&
       !service_worker_context) {
     service_worker_context = request_info->service_worker_context();
   }
 
   if (!service_worker_context)
     return;
 
+  ServiceWorkerProviderHost* provider_host =
+      ServiceWorkerRequestHandler::GetProviderHost(request);
+
+  // If fetched from a service worker, make sure fetching service worker is
+  // controlling at least one client.

[falken, 2016/11/21 04:13:42]

nit: maybe it'd help the reader to add "To prevent a service worker from
spawning new service workers in the background" as in the CL description.

[Marijn Kruisselbrink, 2016/11/21 05:10:56]

Done

+  if (provider_host && provider_host->IsHostToRunningServiceWorker()) {
+    if (!provider_host->running_hosted_version()->HasControllee())
+      return;
+  }
+
   if (ServiceWorkerUtils::IsMainResourceType(request_info->GetResourceType())) {
     // In case of navigations, make sure the navigation will actually result in
     // a secure context.
-    ServiceWorkerProviderHost* provider_host =
-        ServiceWorkerRequestHandler::GetProviderHost(request);
     if (!provider_host || !provider_host->IsContextSecureForServiceWorker())
       return;
   } else {
     // If this is not a navigation, make sure the request was initiated from a
     // secure context.
     if (!request_info->initiated_in_secure_context())
       return;
   }
 
   // TODO(mek): support for a serviceworker link on a request that wouldn't ever
@@ skipping 80 matching lines @@
     const net::URLRequest* request,
     const std::string& link_header,
     ServiceWorkerContextWrapper* service_worker_context_for_testing) {
   for (const auto& value : link_header_util::SplitLinkHeader(link_header)) {
     ProcessLinkHeaderValueForRequest(request, value.first, value.second,
                                      service_worker_context_for_testing);
   }
 }
 
 }  // namespace content