Cache JumpList icons to avoid unnecessary creation and deletion

chrome/browser/win/jumplist.h

 // 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.
 
 #ifndef CHROME_BROWSER_WIN_JUMPLIST_H_
 #define CHROME_BROWSER_WIN_JUMPLIST_H_
 
 #include <stddef.h>
 
 #include <list>
 #include <memory>
 #include <string>
 #include <utility>
 
+#include "base/containers/flat_map.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string16.h"
 #include "base/synchronization/lock.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/prefs/incognito_mode_prefs.h"
 #include "chrome/browser/win/jumplist_updater.h"
 #include "components/history/core/browser/history_service.h"
 #include "components/history/core/browser/history_types.h"
 #include "components/history/core/browser/top_sites_observer.h"
 #include "components/keyed_service/core/refcounted_keyed_service.h"
 #include "components/sessions/core/tab_restore_service.h"
 #include "components/sessions/core/tab_restore_service_observer.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
+enum JumpListCategory { MOST_VISITED = 0, RECENTLY_CLOSED };

[grt (UTC plus 2), 2017/05/11 20:29:13]

nit: Chromium no longer deviates from the Google style for enumerator names, so
please make these kLikeAConstant rather than LIKE_A_MACRO
(https://google.github.io/styleguide/cppguide.html#Enumerator_Names).

[grt (UTC plus 2), 2017/05/11 20:29:13]

move this type into the "private:" section of the class.

[grt (UTC plus 2), 2017/05/11 20:29:13]

nit: "enum class"

[chengx, 2017/05/12 01:04:24]

Done with moving to private section of the class.

[chengx, 2017/05/12 01:04:24]

Done with changing names to kLikeAConstant alike. Thanks for pointing me to
this.

[chengx, 2017/05/12 01:04:24]

Done. Using "enum class" now.

+
 namespace base {
 class SingleThreadTaskRunner;
 class SequencedTaskRunner;
 }
 
 namespace chrome {
 struct FaviconImageResult;
 }
 
 class JumpListFactory;
@@ skipping 127 matching lines @@
                        ChangeReason change_reason) override;
 
   // Called on a timer to update the most visited URLs after requests storms
   // have subsided.
   void DeferredTopSitesChanged();
 
   // Called on a timer to update the "Recently Closed" category of JumpList
   // after requests storms have subsided.
   void DeferredTabRestoreServiceChanged();
 
+  // Deletes icon files in |icon_dir| which are not in the cache anymore.
+  void DeleteIconFiles(const base::FilePath& icon_dir,
+                       JumpListCategory category);
+
   // Creates at most |max_items| icon files in |icon_dir| for the
   // asynchrounously loaded icons stored in |item_list|.
   void CreateIconFiles(const base::FilePath& icon_dir,
                        const ShellLinkItemList& item_list,
-                       size_t max_items);
+                       size_t max_items,
+                       JumpListCategory category);
 
   // Updates icon files in |icon_dir|, which includes deleting old icons and
   // creating at most |slot_limit| new icons for |page_list|.
   void UpdateIconFiles(const base::FilePath& icon_dir,
                        const ShellLinkItemList& page_list,
-                       size_t slot_limit);
+                       size_t slot_limit,
+                       JumpListCategory category);
 
   // Updates the jumplist, once all the data has been fetched. This method calls
   // UpdateJumpList() to do most of the work.
   void RunUpdateJumpList(
       IncognitoModePrefs::Availability incognito_availability,
       const base::string16& app_id,
       const base::FilePath& profile_dir,
       base::RefCountedData<JumpListData>* ref_counted_data);
 
   // Updates the application JumpList, which consists of 1) delete old icon
   // files; 2) create new icon files; 3) notify the OS. This method is called
   // from RunUpdateJumpList().
   // Note that any timeout error along the way results in the old jumplist being
   // left as-is, while any non-timeout error results in the old jumplist being
   // left as-is, but without icon files.
   bool UpdateJumpList(const base::string16& app_id,
                       const base::FilePath& profile_dir,
                       const ShellLinkItemList& most_visited_pages,
                       const ShellLinkItemList& recently_closed_pages,
                       bool most_visited_pages_have_updates,
                       bool recently_closed_pages_have_updates,
                       IncognitoModePrefs::Availability incognito_availability);
 
   // Tracks FaviconService tasks.
   base::CancelableTaskTracker cancelable_task_tracker_;
 
-  // The Profile object is used to listen for events
+  // The Profile object is used to listen for events.
   Profile* profile_;
 
   // Lives on the UI thread.
   std::unique_ptr<PrefChangeRegistrar> pref_change_registrar_;
 
   // App id to associate with the jump list.
   base::string16 app_id_;
 
   // Timer for requesting delayed updates of the "Most Visited" category of
   // jumplist.
   base::OneShotTimer timer_most_visited_;
 
   // Timer for requesting delayed updates of the "Recently Closed" category of
   // jumplist.
   base::OneShotTimer timer_recently_closed_;
 
   // Holds data that can be accessed from multiple threads.
   scoped_refptr<base::RefCountedData<JumpListData>> jumplist_data_;
 
+  // Cache of the mappings from JumpList items' URLs to icon file paths for
+  // "Most visited" and "Recently closed" categories, respectively.
+  base::flat_map<std::string, base::FilePath> most_visited_map_;
+  base::flat_map<std::string, base::FilePath> recently_closed_map_;
+
   // Id of last favicon task. It's used to cancel current task if a new one
   // comes in before it finishes.
   base::CancelableTaskTracker::TaskId task_id_;
 
   // A task runner running tasks to update the JumpList.
   scoped_refptr<base::SingleThreadTaskRunner> update_jumplist_task_runner_;
 
   // A task runner running tasks to delete JumpListIcons directory and
   // JumpListIconsOld directory.
   scoped_refptr<base::SequencedTaskRunner> delete_jumplisticons_task_runner_;
 
   // For callbacks may be run after destruction.
   base::WeakPtrFactory<JumpList> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(JumpList);
 };
 
 #endif  // CHROME_BROWSER_WIN_JUMPLIST_H_