Allow favicons for synced bookmarks to expire

components/history/core/browser/history_backend.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.
 
 #include "components/history/core/browser/history_backend.h"
 
 #include <algorithm>
 #include <functional>
 #include <list>
 #include <map>
@@ skipping 1584 matching lines @@
 
   std::vector<FaviconBitmapIDSize> bitmap_id_sizes;
   thumbnail_db_->GetFaviconBitmapIDSizes(favicon_id, &bitmap_id_sizes);
 
   // If there is already a favicon bitmap of |pixel_size| at |icon_url|,
   // replace it.
   bool bitmap_identical = false;
   bool replaced_bitmap = false;
   for (size_t i = 0; i < bitmap_id_sizes.size(); ++i) {
     if (bitmap_id_sizes[i].pixel_size == pixel_size) {
       if (IsFaviconBitmapDataEqual(bitmap_id_sizes[i].bitmap_id, bitmap_data)) {

[sky, 2015/05/18 17:15:20]

How about a comment as to why this doesn't update the time?

-        thumbnail_db_->SetFaviconBitmapLastUpdateTime(
-            bitmap_id_sizes[i].bitmap_id, base::Time::Now());
+        // TODO: Pass in boolean to MergeFavicon() if any users of
+        // MergeFavicon() want the last_updated time to be updated when the new
+        // bitmap data is identical to the old.
         bitmap_identical = true;
       } else {
         // Expire the favicon bitmap because sync can provide incorrect
         // |bitmap_data|. See crbug.com/474421 for more details. Expiring the
         // favicon bitmap causes it to be redownloaded the next time that the
         // user visits any page which uses |icon_url|.
         thumbnail_db_->SetFaviconBitmap(bitmap_id_sizes[i].bitmap_id,
                                         bitmap_data, base::Time());
         replaced_bitmap = true;
       }
@@ skipping 1021 matching lines @@
   return true;
 }
 
 HistoryClient* HistoryBackend::GetHistoryClient() {
   if (history_client_)
     history_client_->BlockUntilBookmarksLoaded();
   return history_client_;
 }
 
 }  // namespace history