Fix issues and feature polishing for parallel download.

content/browser/download/download_create_info.h

Index: content/browser/download/download_create_info.h
diff --git a/content/browser/download/download_create_info.h b/content/browser/download/download_create_info.h
index 29f5256f13774ae0996deba395ab866457afa365..f5c11ea0a23e5b749fd27edaed9dd04c03ee53b1 100644
--- a/content/browser/download/download_create_info.h
+++ b/content/browser/download/download_create_info.h
@@ -64,12 +64,15 @@ struct CONTENT_EXPORT DownloadCreateInfo {
   // presented or can't be parse, set to 0.
   int64_t total_bytes;
 
-  // The starting position of the request to save to the target file.
+  // The starting position of the initial request.
   // This value matches the offset in DownloadSaveInfo.
-  // TODO(xingliu): Remove this after we refactor DownloadJob to own
-  // DownloadFile.
+  // TODO(xingliu): Refactor to remove |offset| and |length|.
   int64_t offset;
 
+  // The length of the initial request.
+  // This value matches the length in DownloadSaveInfo.
+  int64_t length;

[qinmin, 2017/03/31 17:56:09]

the initial request is always half open, right? why we need this?

[xingliu, 2017/03/31 21:46:10]

Done, addressed in
https://codereview.chromium.org/2789623005/

Also removed the logic to send requests for slices before initial request. Just
use a DCHECK now.

+
   // True if the download was initiated by user action.
   bool has_user_gesture;