Download resumption - Preliminary

content/browser/download/download_file_impl.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.
 
 #include "content/browser/download/download_file_impl.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/file_util.h"
@@ skipping 121 matching lines @@
 void DownloadFileImpl::Detach(base::Closure callback) {
   // Doing the annotation here leaves a small window during
   // which the file has the final name but hasn't been marked with the
   // Mark Of The Web.  However, it allows anti-virus scanners on Windows
   // to actually see the data (http://crbug.com/127999), and the Window
   // is pretty small (round trip to the UI thread).
   AnnotateWithSourceInformation();
 
   file_.Detach();
 
-  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, callback);
+  if (!callback.is_null())
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, callback);
 }
 
 void DownloadFileImpl::Cancel() {
   file_.Cancel();
 }
 
 void DownloadFileImpl::AnnotateWithSourceInformation() {
   bound_net_log_.BeginEvent(net::NetLog::TYPE_DOWNLOAD_FILE_ANNOTATED);
   file_.AnnotateWithSourceInformation();
   bound_net_log_.EndEvent(net::NetLog::TYPE_DOWNLOAD_FILE_ANNOTATED);
@@ skipping 154 matching lines @@
   }
 }
 
 void DownloadFileImpl::SendUpdate() {
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
       base::Bind(&DownloadManager::UpdateDownload,
                  download_manager_, id_.local(),
                  BytesSoFar(), CurrentSpeed(), GetHashState()));
 }