[Download Notification] Show preview if downloaded file is image

chrome/browser/download/notification/download_notification_item.h

 // Copyright 2015 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.
 
 #ifndef CHROME_BROWSER_DOWNLOAD_NOTIFICATION_DOWNLOAD_NOTIFICATION_ITEM_H_
 #define CHROME_BROWSER_DOWNLOAD_NOTIFICATION_DOWNLOAD_NOTIFICATION_ITEM_H_
 
 #include "chrome/browser/download/notification/download_notification_item.h"
 
 #include "base/strings/string_number_conversions.h"
@@ skipping 68 matching lines @@
 
   // DownloadItem::Observer overrides:
   void OnDownloadUpdated(content::DownloadItem* item) override;
   void OnDownloadOpened(content::DownloadItem* item) override;
   void OnDownloadRemoved(content::DownloadItem* item) override;
   void OnDownloadDestroyed(content::DownloadItem* item) override;
 
   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;
 
   // Returns a short one-line status string for the download.
   base::string16 GetTitle() const;
 
   // Returns a short one-line status string for a download command.
   base::string16 GetCommandLabel(DownloadCommands::Command command) const;
 
   // Get the warning test to notify a dangerous download. Should only be called
   // if IsDangerous() is true.
   base::string16 GetWarningText() const;
 
   Browser* GetBrowser();
 
   // Returns the list of possible extra (all except the default) actions.
   scoped_ptr<std::vector<DownloadCommands::Command>> GetExtraActions() const;
 
   int image_resource_id_ = 0;
   content::DownloadItem::DownloadState previous_download_state_ =
       content::DownloadItem::MAX_DOWNLOAD_STATE;  // As uninitialized state
   Profile* profile_;
   scoped_refptr<NotificationWatcher> watcher_;
   scoped_ptr<Notification> notification_;
   content::DownloadItem* item_;
   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);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_NOTIFICATION_DOWNLOAD_NOTIFICATION_ITEM_H_