[Downloads] Use the initiating StoragePartition for resumption.

components/history/core/browser/download_row.h

Index: components/history/core/browser/download_row.h
diff --git a/components/history/core/browser/download_row.h b/components/history/core/browser/download_row.h
index d1a6214e42c8df9a20436c4be7f533230e4b1d60..b0ad5d01374a44dbd91b64fa329236eb72446b74 100644
--- a/components/history/core/browser/download_row.h
+++ b/components/history/core/browser/download_row.h
@@ -26,6 +26,7 @@ struct DownloadRow {
               const base::FilePath& target_path,
               const std::vector<GURL>& url_chain,
               const GURL& referrer_url,
+              const GURL& site_instance_url,
               const GURL& tab_url,
               const GURL& tab_referrer_url,
               const std::string& http_method,
@@ -67,6 +68,9 @@ struct DownloadRow {
   // The URL that referred us. Is not changed by UpdateDownload().
   GURL referrer_url;
 
+  // The site URL for the site instance that initiated the download.
+  GURL site_instance_url;
+
   // The URL of the tab that initiated the download, if any. Not changed by
   // UpdateDownload().
   GURL tab_url;