set content length limit if half open range request fails

content/browser/download/download_file_impl.h

Index: content/browser/download/download_file_impl.h
diff --git a/content/browser/download/download_file_impl.h b/content/browser/download/download_file_impl.h
index e786c2b38b0fff0400e9f4d9bed85463b60b22b9..47c644ed3d9b659472788dacb9ed33c37ed26c45 100644
--- a/content/browser/download/download_file_impl.h
+++ b/content/browser/download/download_file_impl.h
@@ -69,6 +69,7 @@ class CONTENT_EXPORT DownloadFileImpl : public DownloadFile {
                          const RenameCompletionCallback& callback) override;
   void Detach() override;
   void Cancel() override;
+  void SetContentLengthLimit(int64_t limit) override;
   const base::FilePath& FullPath() const override;
   bool InProgress() const override;
   void WasPaused() override;
@@ -251,6 +252,9 @@ class CONTENT_EXPORT DownloadFileImpl : public DownloadFile {
   // Used to trigger progress updates.
   std::unique_ptr<base::RepeatingTimer> update_timer_;
 
+  // Maximum length of the file, -1 if the limit is unknown.

[xingliu, 2017/03/31 23:38:21]

nit%: It's a bit confusing that people might think this is a copy of the
Content-Length header.

[qinmin, 2017/04/01 05:20:02]

it is different, the limit is the upper bound, the actual file size could be
smaller than this. 
changed the variable name to potential_file_length_

[xingliu, 2017/04/03 16:51:56]

Thanks.

+  int64_t content_length_limit_;
+
   // Statistics
   size_t bytes_seen_;
   base::TimeDelta disk_writes_time_;