Fix an issue that we didn't clean url request properly.

content/browser/download/download_file.h

Index: content/browser/download/download_file.h
diff --git a/content/browser/download/download_file.h b/content/browser/download/download_file.h
index 224121a034b77a1073b4ec7923a1e9f6e94b83d4..24dc4f3bfe1f7a9294b47de526682d3f91723b21 100644
--- a/content/browser/download/download_file.h
+++ b/content/browser/download/download_file.h
@@ -42,13 +42,18 @@ class CONTENT_EXPORT DownloadFile {
                               const base::FilePath& path)>
       RenameCompletionCallback;
 
+  // Used to drop the request, when the byte stream reader should be closed on
+  // FILE thread.
+  typedef base::Callback<void(int64_t offset)> CancelRequestCallback;
+
   virtual ~DownloadFile() {}
 
   // Upon completion, |callback| will be called on the UI

[qinmin, 2017/04/17 21:39:59]

s/callback/initialize_callback/

[xingliu, 2017/04/17 23:41:51]

Done.

   // thread as per the comment above, passing DOWNLOAD_INTERRUPT_REASON_NONE
   // on success, or a network download interrupt reason on failure.
   virtual void Initialize(
-      const InitializeCallback& callback,
+      const InitializeCallback& initialize_callback,
+      const CancelRequestCallback& cancel_request_callback,
       const DownloadItem::ReceivedSlices& received_slices) = 0;
 
   // Add a byte stream reader to write into a slice of the file, used for