[Downloads] Rework how hashes are calculated for download files.

chrome/browser/download/download_history.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // DownloadHistory manages persisting DownloadItems to the history service by
 // observing a single DownloadManager and all its DownloadItems using an
 // AllDownloadItemNotifier.
 //
 // DownloadHistory decides whether and when to add items to, remove items from,
 // and update items in the database. DownloadHistory uses DownloadHistoryData to
@@ skipping 246 matching lines @@
 
 void DownloadHistory::QueryCallback(scoped_ptr<InfoVector> infos) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   // ManagerGoingDown() may have happened before the history loaded.
   if (!notifier_.GetManager())
     return;
   for (InfoVector::const_iterator it = infos->begin();
        it != infos->end(); ++it) {
     loading_id_ = history::ToContentDownloadId(it->id);
     content::DownloadItem* item = notifier_.GetManager()->CreateDownloadItem(
-        loading_id_,
-        it->current_path,
-        it->target_path,
-        it->url_chain,
-        it->referrer_url,
-        it->mime_type,
-        it->original_mime_type,
-        it->start_time,
-        it->end_time,
-        it->etag,
-        it->last_modified,
-        it->received_bytes,
+        loading_id_, it->current_path, it->target_path, it->url_chain,

[svaldez, 2016/03/09 19:27:33]

nit: Might want to revert the formatting, though no strong opinion.

[asanka, 2016/03/10 16:48:08]

'git cl format' :-( I like the previous formatting too, but trying to preserve
it is a losing battle. Anytime someone touches some code nearby and run 'git cl
format' we are going to end up with this.

+        it->referrer_url, it->mime_type, it->original_mime_type, it->start_time,
+        it->end_time, it->etag, it->last_modified, it->received_bytes,
         it->total_bytes,
+        std::string(),  // TODO(asanka): Need to persist and restore hash of
+                        // partial file for an interrupted download. No need to
+                        // store hash for a completed file.
         history::ToContentDownloadState(it->state),
         history::ToContentDownloadDangerType(it->danger_type),
         history::ToContentDownloadInterruptReason(it->interrupt_reason),
         it->opened);
 #if defined(ENABLE_EXTENSIONS)
     if (!it->by_ext_id.empty() && !it->by_ext_name.empty()) {
       new extensions::DownloadedByExtension(
           item, it->by_ext_id, it->by_ext_name);
       item->UpdateObservers();
     }
@@ skipping 170 matching lines @@
   removing_ids_.insert(download_id);
 }
 
 void DownloadHistory::RemoveDownloadsBatch() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   IdSet remove_ids;
   removing_ids_.swap(remove_ids);
   history_->RemoveDownloads(remove_ids);
   FOR_EACH_OBSERVER(Observer, observers_, OnDownloadsRemoved(remove_ids));
 }