[NTP] Propagate OfflineId from C++ for Downloads.

components/ntp_snippets/content_suggestion.h

Index: components/ntp_snippets/content_suggestion.h
diff --git a/components/ntp_snippets/content_suggestion.h b/components/ntp_snippets/content_suggestion.h
index 630b7e5ad65efe1740c13d78cd0807a3dea7a7d5..523ea7cccbf452c16390e96390e23f1238385959 100644
--- a/components/ntp_snippets/content_suggestion.h
+++ b/components/ntp_snippets/content_suggestion.h
@@ -20,11 +20,18 @@ namespace ntp_snippets {
 // DownloadSuggestionExtra contains additional data which is only available for
 // download suggestions.
 struct DownloadSuggestionExtra {
+  DownloadSuggestionExtra();   // = default, in .cc

[Bernhard Bauer, 2016/11/16 17:44:35]

I don't think you need to specify how the implementation file chooses to
implement these.

[vitaliii, 2016/11/16 18:15:22]

Done.

+  ~DownloadSuggestionExtra();  // = default, in .cc
+
   // The file path of the downloaded file once download completes.
   base::FilePath target_file_path;
   // The effective MIME type of downloaded content.
   std::string mime_type;
+  // Underlying offline page identifier.
+  int64_t offline_page_id;

[Bernhard Bauer, 2016/11/16 17:44:35]

Maybe initialize this to 0 now?

[vitaliii, 2016/11/16 18:15:22]

Done.

   // Whether or not the download suggestion is a downloaded asset.
+  // When this is true, |offline_page_id| is ignored, otherwise
+  // |target_file_path| and |mime_type| are ignored.
   bool is_download_asset = false;
 };
 
@@ -33,7 +40,7 @@ struct RecentTabSuggestionExtra {
   // Corresponding tab identifier.
   std::string tab_id;
   // Underlying offline page identifier.
-  std::string offline_page_id;
+  int64_t offline_page_id;
 };
 
 // A content suggestion for the new tab page, which can be an article or an