Add observing Data::DownloadManager.

Telegram/SourceFiles/data/data_file_click_handler.cpp

@@ -9,7 +9,10 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 
 #include "core/click_handler_types.h"
 #include "core/file_utilities.h"
+#include "core/application.h"
 #include "data/data_document.h"
+#include "data/data_session.h"
+#include "data/data_download_manager.h"
 #include "data/data_photo.h"
 
 FileClickHandler::FileClickHandler(FullMsgId context)
@@ -98,7 +101,17 @@ void DocumentSaveClickHandler::Save(
 }
 
 void DocumentSaveClickHandler::onClickImpl() const {
-	Save(context(), document());
+	const auto document = this->document();
+	const auto itemId = context();
+	Save(itemId, document);
+	if (document->loading()) {
+		if (const auto item = document->owner().message(itemId)) {
+			Core::App().downloadManager().addLoading({
+				.item = item,
+				.document = document,
+			});
+		}
+	}
 }
 
 DocumentCancelClickHandler::DocumentCancelClickHandler(