[Download Notification] Show preview if downloaded file is image

chrome/browser/download/notification/download_notification_item.h

Index: chrome/browser/download/notification/download_notification_item.h
diff --git a/chrome/browser/download/notification/download_notification_item.h b/chrome/browser/download/notification/download_notification_item.h
index 76fb48b9e5a7e4c9d8b96d5f6850b98f4ec504be..225c176f7634b99ddc0c47defd9b95ae9ed6166f 100644
--- a/chrome/browser/download/notification/download_notification_item.h
+++ b/chrome/browser/download/notification/download_notification_item.h
@@ -86,7 +86,12 @@ class DownloadNotificationItem : public content::DownloadItem::Observer {
   void CloseNotificationByUser();
   void CloseNotificationByNonUser();
   void UpdateNotificationData(NotificationUpdateType type);
-  void SetNotificationImage(int resource_id);
+
+  // Set icon of the notification.
+  void SetNotificationIcon(int resource_id);
+
+  // Set preview image of the notification. Must be called on IO thread.
+  void SetNotificationImage(gfx::Image image);
 
   NotificationUIManager* notification_ui_manager() const;
 
@@ -115,6 +120,11 @@ class DownloadNotificationItem : public content::DownloadItem::Observer {
   scoped_ptr<std::vector<DownloadCommands::Command>> button_actions_;
   Delegate* const delegate_;
 
+  // Whether the preview image been has set or not.
+  bool set_image_ = false;
+
+  base::WeakPtrFactory<DownloadNotificationItem> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(DownloadNotificationItem);
 };