Range request support for parallel download in DownloadRequestCore.

content/public/browser/download_save_info.h

Index: content/public/browser/download_save_info.h
diff --git a/content/public/browser/download_save_info.h b/content/public/browser/download_save_info.h
index 69893f4bbd601f76f738644d3c8546d6e57ab8a5..f3db9ee6374db5f02f4db6eb6dfaee5896dbe24b 100644
--- a/content/public/browser/download_save_info.h
+++ b/content/public/browser/download_save_info.h
@@ -22,6 +22,9 @@ namespace content {
 // name, |offset| is set to the point where we left off, and |hash_state| will
 // hold the state of the hash algorithm where we left off.
 struct CONTENT_EXPORT DownloadSaveInfo {
+  // The default value for |length|.
+  static const int kLengthFullContent;

[alexmos, 2017/02/08 06:52:48]

Up to you, but I think you could also just assign this to 0 here.  Would it make
sense to make it int64_t to match the |length| type?  Also, might want to
mention what this is used for in this comment as well.

+
   DownloadSaveInfo();
   ~DownloadSaveInfo();
   DownloadSaveInfo(DownloadSaveInfo&& that);
@@ -41,6 +44,12 @@ struct CONTENT_EXPORT DownloadSaveInfo {
   // The file offset at which to start the download.  May be 0.
   int64_t offset;
 
+  // The length of the bytes from |offset|. Set to |kLengthFullContent| by

[alexmos, 2017/02/08 06:52:48]

nit: The number of bytes to download from |offset|  (just trying to rephrase for
a bit more clarity)

+  // default.
+  // Ask to retrieve segment of the download file when length is greater than 0.
+  // Request the whole file when length is |kLengthFullContent|.

[alexmos, 2017/02/08 06:52:48]

nit: not the "whole file", but the rest of the file starting from |offset|,
right?

+  int64_t length;
+
   // The state of the hash. If specified, this hash state must indicate the
   // state of the partial file for the first |offset| bytes.
   std::unique_ptr<crypto::SecureHash> hash_state;