Cache JumpList icons to avoid unnecessary creation and deletion

chrome/browser/win/jumplist.h

Index: chrome/browser/win/jumplist.h
diff --git a/chrome/browser/win/jumplist.h b/chrome/browser/win/jumplist.h
index c4b6c857584430198509a89a08b224963d7fb3e0..125cd533a8e5a915ae5caecf0ea96eaf1f95eafd 100644
--- a/chrome/browser/win/jumplist.h
+++ b/chrome/browser/win/jumplist.h
@@ -12,6 +12,7 @@
 #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"
@@ -32,6 +33,8 @@
 #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;
@@ -179,17 +182,23 @@ class JumpList : public sessions::TabRestoreServiceObserver,
   // 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.
@@ -216,7 +225,7 @@ class JumpList : public sessions::TabRestoreServiceObserver,
   // 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.
@@ -236,6 +245,11 @@ class JumpList : public sessions::TabRestoreServiceObserver,
   // 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_;