Add support for subresource request fallback in AppCache for the network service..

content/browser/appcache/appcache_request_handler.cc

Index: content/browser/appcache/appcache_request_handler.cc
diff --git a/content/browser/appcache/appcache_request_handler.cc b/content/browser/appcache/appcache_request_handler.cc
index 652eff24a7acf59b8edd790ac25b29a544e3b5f2..b8eaaf2a0419b330b99071b8b8329be3c30b6c0b 100644
--- a/content/browser/appcache/appcache_request_handler.cc
+++ b/content/browser/appcache/appcache_request_handler.cc
@@ -127,19 +127,24 @@ AppCacheJob* AppCacheRequestHandler::MaybeLoadFallbackForRedirect(
   if (request_->GetURL().GetOrigin() == location.GetOrigin())
     return NULL;
 
-  DCHECK(!job_.get());  // our jobs never generate redirects
+  // In network service land, the existing job initiates a fallback request.
+  if (!base::FeatureList::IsEnabled(features::kNetworkService)) {
+    DCHECK(!job_.get());  // our jobs never generate redirects
+  } else {
+    DCHECK(job_.get());
+  }
 
   std::unique_ptr<AppCacheJob> job;
   if (found_fallback_entry_.has_response_id()) {
+    job = MaybeCreateJobForFallback(network_delegate);
     // 6.9.6, step 4: If this results in a redirect to another origin,
     // get the resource of the fallback entry.
-    job = CreateJob(network_delegate);
     DeliverAppCachedResponse(found_fallback_entry_, found_cache_id_,
                              found_manifest_url_, true,
                              found_namespace_entry_url_);
   } else if (!found_network_namespace_) {
     // 6.9.6, step 6: Fail the resource load.
-    job = CreateJob(network_delegate);
+    job = MaybeCreateJobForFallback(network_delegate);
     DeliverErrorResponse();
   } else {
     // 6.9.6 step 3 and 5: Fetch the resource normally.
@@ -163,7 +168,7 @@ AppCacheJob* AppCacheRequestHandler::MaybeLoadFallbackForResponse(
   }
 
   // We don't fallback for responses that we delivered.
-  if (job_.get()) {
+  if (job_.get() && !base::FeatureList::IsEnabled(features::kNetworkService)) {
     DCHECK(!job_->IsDeliveringNetworkResponse());
     return NULL;
   }
@@ -186,7 +191,12 @@ AppCacheJob* AppCacheRequestHandler::MaybeLoadFallbackForResponse(
 
   // 6.9.6, step 4: If this results in a 4xx or 5xx status code
   // or there were network errors, get the resource of the fallback entry.
-  std::unique_ptr<AppCacheJob> job = CreateJob(network_delegate);
+
+  // In network service land, the job initiates a fallback request. We reuse
+  // the existing job to deliver the fallback response.
+  std::unique_ptr<AppCacheJob> job =
+      MaybeCreateJobForFallback(network_delegate);
+
   DeliverAppCachedResponse(found_fallback_entry_, found_cache_id_,
                            found_manifest_url_, true,
                            found_namespace_entry_url_);
@@ -342,6 +352,19 @@ std::unique_ptr<AppCacheJob> AppCacheRequestHandler::CreateJob(
   return job;
 }
 
+std::unique_ptr<AppCacheJob> AppCacheRequestHandler::MaybeCreateJobForFallback(
+    net::NetworkDelegate* network_delegate) {
+  std::unique_ptr<AppCacheJob> job;
+  // In network service land, the job initiates a fallback request. We reuse
+  // the existing job to deliver the fallback response.
+  if (!base::FeatureList::IsEnabled(features::kNetworkService)) {
+    job = CreateJob(network_delegate);
+  } else {
+    job.reset(job_.get());
+  }
+  return job;
+}
+
 // Main-resource handling ----------------------------------------------
 
 std::unique_ptr<AppCacheJob> AppCacheRequestHandler::MaybeLoadMainResource(