Added callback to DownloadUrl() so we can find download failures.

content/browser/renderer_host/resource_dispatcher_host.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/renderer_host/resource_dispatcher_host.h"
 
 #include <set>
 #include <vector>
@@ skipping 286 matching lines @@
   }
 }
 
 void OnSwapOutACKHelper(int render_process_id, int render_view_id) {
   RenderViewHostImpl* rvh = RenderViewHostImpl::FromID(render_process_id,
                                                        render_view_id);
   if (rvh)
     rvh->OnSwapOutACK();
 }
 
+net::Error CallbackAndReturn(
+    const DownloadResourceHandler::OnStartedCallback& started_cb,
+    net::Error net_error) {
+  DCHECK(!started_cb.is_null());

[Randy Smith (Not in Mondays), 2012/03/09 19:14:02]

Why the DCHECK?  This may be a result of my not yet understanding callbacks
thoroughly, but I'm sure it's ok for people to pass in default constructed
callbacks (since you're doing it in this CL); if that translates to null, the
DCHECK shouldn't be here.  If it doesn't translate to null, the DCHECK is fine.

[ahendrickson, 2012/03/09 20:50:08]

Removed.

+  if (started_cb.is_null())
+    return net_error;
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(started_cb, content::DownloadId::Invalid(), net_error));
+
+  return net_error;
+}
+
 }  // namespace
 
 ResourceDispatcherHost* ResourceDispatcherHost::Get() {
   return g_resource_dispatcher_host;
 }
 
 ResourceDispatcherHost::ResourceDispatcherHost()
     : ALLOW_THIS_IN_INITIALIZER_LIST(
           download_file_manager_(new DownloadFileManager(this, NULL))),
       ALLOW_THIS_IN_INITIALIZER_LIST(
@@ skipping 600 matching lines @@
 // We are explicitly forcing the download of 'url'.
 net::Error ResourceDispatcherHost::BeginDownload(
     scoped_ptr<net::URLRequest> request,
     bool prefer_cache,
     const DownloadSaveInfo& save_info,
     const DownloadResourceHandler::OnStartedCallback& started_cb,
     int child_id,
     int route_id,
     content::ResourceContext* context) {
   if (is_shutdown_)
-    return net::ERR_INSUFFICIENT_RESOURCES;
+    return CallbackAndReturn(started_cb, net::ERR_INSUFFICIENT_RESOURCES);
 
   const GURL& url = request->original_url();
 #if defined(OS_CHROMEOS)
   // crosbug.com/26646.
   VLOG(1) << "BeginDownload: " << request->url().spec();
 #endif
   const net::URLRequestContext* request_context = context->GetRequestContext();
   request->set_referrer(MaybeStripReferrer(GURL(request->referrer())).spec());
   request->set_context(request_context);
   int extra_load_flags = net::LOAD_IS_DOWNLOAD;
   if (prefer_cache) {
     // If there is upload data attached, only retrieve from cache because there
     // is no current mechanism to prompt the user for their consent for a
     // re-post. For GETs, try to retrieve data from the cache and skip
     // validating the entry if present.
     if (request->get_upload() != NULL)
       extra_load_flags |= net::LOAD_ONLY_FROM_CACHE;
     else
       extra_load_flags |= net::LOAD_PREFERRING_CACHE;
   } else {
     extra_load_flags |= net::LOAD_DISABLE_CACHE;
   }
   request->set_load_flags(request->load_flags() | extra_load_flags);
   // Check if the renderer is permitted to request the requested URL.
   if (!ChildProcessSecurityPolicyImpl::GetInstance()->
           CanRequestURL(child_id, url)) {
     VLOG(1) << "Denied unauthorized download request for "
             << url.possibly_invalid_spec();
-    return net::ERR_ACCESS_DENIED;
+    return CallbackAndReturn(started_cb, net::ERR_ACCESS_DENIED);
   }
 
   request_id_--;
 
+  // From this point forward, the |DownloadResourceHandler| is responsible for
+  // |started_cb|.
   scoped_refptr<ResourceHandler> handler(
       CreateResourceHandlerForDownload(request.get(), context, child_id,
                                        route_id, request_id_, save_info,
                                        started_cb));
 
   if (!request_context->job_factory()->IsHandledURL(url)) {
     VLOG(1) << "Download request for unsupported protocol: "
             << url.possibly_invalid_spec();
     return net::ERR_ACCESS_DENIED;
   }
@@ skipping 1308 matching lines @@
   scoped_refptr<ResourceHandler> transferred_resource_handler(
       new DoomedResourceHandler(info->resource_handler()));
   info->set_resource_handler(transferred_resource_handler.get());
 }
 
 bool ResourceDispatcherHost::IsTransferredNavigation(
     const content::GlobalRequestID& transferred_request_id) const {
   return transferred_navigations_.find(transferred_request_id) !=
       transferred_navigations_.end();
 }