Revert of Refactor History's CommitLaterTask with CancelableCallback

components/history/core/browser/history_backend.h

Index: components/history/core/browser/history_backend.h
diff --git a/components/history/core/browser/history_backend.h b/components/history/core/browser/history_backend.h
index 82166f7e721a3c5d8d0667429b39ad39487e7238..6959994ab1ae814988b99a55bda09e7a17a89aaf 100644
--- a/components/history/core/browser/history_backend.h
+++ b/components/history/core/browser/history_backend.h
@@ -14,7 +14,6 @@
 #include <utility>
 #include <vector>
 
-#include "base/cancelable_callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/containers/mru_cache.h"
 #include "base/files/file_path.h"
@@ -43,6 +42,7 @@
 }
 
 namespace history {
+class CommitLaterTask;
 struct DownloadRow;
 class HistoryBackendClient;
 class HistoryBackendDBBaseTest;
@@ -480,6 +480,7 @@
 
  private:
   friend class base::RefCountedThreadSafe<HistoryBackend>;
+  friend class CommitLaterTask;  // The commit task needs to call Commit().
   friend class HistoryBackendTest;
   friend class HistoryBackendDBBaseTest;  // So the unit tests can poke our
                                           // innards.
@@ -827,11 +828,10 @@
   ExpireHistoryBackend expirer_;
 
   // A commit has been scheduled to occur sometime in the future. We can check
-  // !IsCancelled() to see if there is a commit scheduled in the future (note
-  // that CancelableClosure starts cancelled with the default constructor), and
-  // we can use Cancel() to cancel the scheduled commit. There can be only one
+  // non-null-ness to see if there is a commit scheduled in the future, and we
+  // can use the pointer to cancel the scheduled commit. There can be only one
   // scheduled commit at a time (see ScheduleCommit).
-  base::CancelableClosure scheduled_commit_;
+  scoped_refptr<CommitLaterTask> scheduled_commit_;
 
   // Maps recent redirect destination pages to the chain of redirects that
   // brought us to there. Pages that did not have redirects or were not the