The Appcache subresource URL factory needs to inform the URLLoaderClient if there is a failure.

content/browser/appcache/appcache_subresource_url_factory.cc

Index: content/browser/appcache/appcache_subresource_url_factory.cc
diff --git a/content/browser/appcache/appcache_subresource_url_factory.cc b/content/browser/appcache/appcache_subresource_url_factory.cc
index 4b6f9fd36b56372749525dd7296dfdc9fb592209..7cf3e200ec1592c4ce28ffe227893c2fd2468228 100644
--- a/content/browser/appcache/appcache_subresource_url_factory.cc
+++ b/content/browser/appcache/appcache_subresource_url_factory.cc
@@ -21,6 +21,13 @@
 
 namespace content {
 
+namespace {
+
+// Set to true if we are running as part of tests.
+bool g_for_testing = false;
+
+}  // namespace.
+
 // Implements the URLLoaderFactory mojom for AppCache requests.
 AppCacheSubresourceURLFactory::AppCacheSubresourceURLFactory(
     mojom::URLLoaderFactoryRequest request,
@@ -63,17 +70,17 @@ void AppCacheSubresourceURLFactory::CreateLoaderAndStart(
 
   // If the host is invalid, it means that the renderer has probably died.
   // (Frame has navigated elsewhere?)
-  if (!appcache_host_.get())
+  if (!appcache_host_.get() && !g_for_testing) {
+    NotifyError(std::move(client), net::ERR_FAILED);
     return;
+  }
 
   std::unique_ptr<AppCacheRequestHandler> handler =
       appcache_host_->CreateRequestHandler(
           AppCacheURLLoaderRequest::Create(request), request.resource_type,
           request.should_reset_appcache);
   if (!handler) {
-    ResourceRequestCompletionStatus request_result;
-    request_result.error_code = net::ERR_FAILED;
-    client->OnComplete(request_result);
+    NotifyError(std::move(client), net::ERR_FAILED);
     return;
   }
 
@@ -109,4 +116,17 @@ void AppCacheSubresourceURLFactory::OnConnectionError() {
   base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, this);
 }
 
+void AppCacheSubresourceURLFactory::NotifyError(
+    mojom::URLLoaderClientPtr client,
+    int error_code) {
+  ResourceRequestCompletionStatus request_result;
+  request_result.error_code = error_code;
+  client->OnComplete(request_result);
+}
+
+// static
+void AppCacheSubresourceURLFactory::SetForTesting(bool for_testing) {
+  g_for_testing = for_testing;
+}
+
 }  // namespace content