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

content/browser/renderer_host/resource_dispatcher_host.cc

Index: content/browser/renderer_host/resource_dispatcher_host.cc
diff --git a/content/browser/renderer_host/resource_dispatcher_host.cc b/content/browser/renderer_host/resource_dispatcher_host.cc
index ef9e225487f968feccbfee012e6aecc444760374..5280743816436cbe2545e399bf706477d9487048 100644
--- a/content/browser/renderer_host/resource_dispatcher_host.cc
+++ b/content/browser/renderer_host/resource_dispatcher_host.cc
@@ -301,6 +301,24 @@ void OnSwapOutACKHelper(int render_process_id, int render_view_id) {
     rvh->OnSwapOutACK();
 }
 
+void CallbackOnUIThread(
+    const DownloadResourceHandler::OnStartedCallback& started_cb,
+    net::Error net_error) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  started_cb.Run(content::DownloadId::Invalid(), net_error);
+}
+
+net::Error CallbackAndReturn(
+    const DownloadResourceHandler::OnStartedCallback& started_cb,
+    net::Error net_error) {
+  BrowserThread::PostTask(

[cbentzel, 2012/03/08 17:58:48]

Skip this if started_cb.is_null()?

[ahendrickson, 2012/03/08 21:33:07]

Done.

+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&CallbackOnUIThread, started_cb, net_error));

[Randy Smith (Not in Mondays), 2012/03/07 21:16:57]

Can you just bind started_cb to content::DownloadId::Invalid(), net_error and
post that callback to the UI thread, skipping CallbackOnUIThread?

[ahendrickson, 2012/03/08 21:33:07]

Done.

+
+  return net_error;
+}
+
 }  // namespace
 
 ResourceDispatcherHost* ResourceDispatcherHost::Get() {
@@ -916,7 +934,7 @@ net::Error ResourceDispatcherHost::BeginDownload(
     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();
   const net::URLRequestContext* request_context = context->GetRequestContext();
@@ -941,7 +959,7 @@ net::Error ResourceDispatcherHost::BeginDownload(
           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_--;
@@ -954,7 +972,7 @@ net::Error ResourceDispatcherHost::BeginDownload(
   if (!request_context->job_factory()->IsHandledURL(url)) {
     VLOG(1) << "Download request for unsupported protocol: "
             << url.possibly_invalid_spec();
-    return net::ERR_ACCESS_DENIED;
+    return CallbackAndReturn(started_cb, net::ERR_ACCESS_DENIED);

[Randy Smith (Not in Mondays), 2012/03/07 21:16:57]

Since you've already created the resource handler at this point, I think you'll
get a double callback (one from the DRH destructor).  (If you agree and fix
this, I'd add a comment above about passing responsibility for the callback to
the DRH.)

[ahendrickson, 2012/03/08 21:33:07]

Done.

   }
 
   ResourceDispatcherHostRequestInfo* extra_info =