Migrate jumplist update task from FILE thread to base/task_scheduler

chrome/browser/win/jumplist_file_util.cc

Index: chrome/browser/win/jumplist_file_util.cc
diff --git a/chrome/browser/win/jumplist_file_util.cc b/chrome/browser/win/jumplist_file_util.cc
index 66d9651a64ba3e4347b8eb7ffe1eee8128d2f532..cb405fdecdfb48b9c8ed1ff23dad9f8554cc9b91 100644
--- a/chrome/browser/win/jumplist_file_util.cc
+++ b/chrome/browser/win/jumplist_file_util.cc
@@ -109,13 +109,14 @@ FolderDeleteResult DeleteDirectory(const base::FilePath& path,
 
 void DeleteDirectoryAndLogResults(const base::FilePath& path,
                                   int max_file_deleted) {
-  FolderDeleteResult delete_status = DeleteDirectory(path, max_file_deleted);
-  UMA_HISTOGRAM_ENUMERATION("WinJumplist.DeleteStatusJumpListIconsOld",
-                            delete_status, END);
-
   DirectoryStatus dir_status = NON_EXIST;
-  if (base::DirectoryExists(path))
+
+  if (base::DirectoryExists(path)) {
+    FolderDeleteResult delete_status = DeleteDirectory(path, max_file_deleted);
+    UMA_HISTOGRAM_ENUMERATION("WinJumplist.DeleteStatusJumpListIconsOld",

[gab, 2017/04/04 21:11:46]

Why do we need a separate histogram? Why isn't histograms.xml modified
accordingly?

[chengx, 2017/04/05 00:23:24]

JumpListIcons folder and JumpListIconsOld folder operation are now completely
independent of each other, and JumpListIconsOld will be gone eventually. Using
two histograms allows independent analysis of the two folder operations in a
much clearer way.

[gab, 2017/04/05 20:53:26]

I see, hadn't noticed the different enums, prefixing with
FolderDeleteResult::END could help there.

Also, new histograms.xml entry?

+                              delete_status, END);
     dir_status = base::IsDirectoryEmpty(path) ? EMPTY : NON_EMPTY;
+  }
 
   UMA_HISTOGRAM_ENUMERATION("WinJumplist.DirectoryStatusJumpListIconsOld",
                             dir_status, DIRECTORY_STATUS_END);