Add control to use If-Range header for range request.

content/browser/download/download_request_core.h

Index: content/browser/download/download_request_core.h
diff --git a/content/browser/download/download_request_core.h b/content/browser/download/download_request_core.h
index 4fc3f7536130719c20ec457d7ef11ca739ef15ea..34b12893b39ec081b9dddda6be833b7551571864 100644
--- a/content/browser/download/download_request_core.h
+++ b/content/browser/download/download_request_core.h
@@ -122,6 +122,9 @@ class CONTENT_EXPORT DownloadRequestCore
       const net::HttpResponseHeaders& http_headers,
       DownloadSaveInfo* save_info);
 
+  static void AddPartialRequestHeaders(net::URLRequest* request,
+                                       DownloadUrlParameters* params);
+
   std::unique_ptr<DownloadCreateInfo> CreateDownloadCreateInfo(
       DownloadInterruptReason result);