[Offline pages] Fixing crash happening when 2 pages get saved about the same time

components/offline_pages/downloads/download_ui_adapter.cc

Index: components/offline_pages/downloads/download_ui_adapter.cc
diff --git a/components/offline_pages/downloads/download_ui_adapter.cc b/components/offline_pages/downloads/download_ui_adapter.cc
index 1ef3534dba10ccb046ae8e1894f32ae606d9ff24..eff4b50c40cdfe771080aa63f3c7d4d610c7d873 100644
--- a/components/offline_pages/downloads/download_ui_adapter.cc
+++ b/components/offline_pages/downloads/download_ui_adapter.cc
@@ -198,8 +198,6 @@ void DownloadUIAdapter::OnOfflinePagesChanged(
     items_[guid] = base::MakeUnique<ItemInfo>(page);
     added_guids.push_back(guid);
   }
-  // Only one added page
-  CHECK(added_guids.size() <= 1);
   for (auto& guid : added_guids) {
     const DownloadUIItem& item = *(items_.find(guid)->second->ui_item.get());
     FOR_EACH_OBSERVER(Observer, observers_, ItemAdded(item));