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 6959994ab1ae814988b99a55bda09e7a17a89aaf..f05663412f3262932794f305ec444c1e6f116c55 100644
--- a/components/history/core/browser/history_backend.h
+++ b/components/history/core/browser/history_backend.h
@@ -14,6 +14,7 @@
 #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"
@@ -42,7 +43,6 @@ class SingleThreadTaskRunner;
 }
 
 namespace history {
-class CommitLaterTask;
 struct DownloadRow;
 class HistoryBackendClient;
 class HistoryBackendDBBaseTest;
@@ -480,7 +480,6 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
 
  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.
@@ -828,10 +827,10 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   ExpireHistoryBackend expirer_;
 
   // A commit has been scheduled to occur sometime in the future. We can check
-  // 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
+  // !IsCancelled() to see if there is a commit scheduled in the future, and we
+  // can use Cancel() to cancel the scheduled commit. There can be only one

[brettw, 2017/02/08 04:58:30]

Can you mention here that the initial state for a default-initialized
CancelableClosure is "canceled"? I had to go check the semantics because I was
suspicious of your unconditional usage of IsCanceled in the code.

[mastiz, 2017/02/08 08:04:29]

Done. I had a comment in the .cc file about this, added it here as well now.

   // scheduled commit at a time (see ScheduleCommit).
-  scoped_refptr<CommitLaterTask> scheduled_commit_;
+  base::CancelableClosure 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