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..42b222f68dbab950834b2931eca157ff112ced4e 100644
--- a/components/history/core/browser/history_backend.h
+++ b/components/history/core/browser/history_backend.h
@@ -14,12 +14,14 @@
 #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"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/memory_pressure_listener.h"
+#include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/single_thread_task_runner.h"
 #include "base/supports_user_data.h"
@@ -42,7 +44,6 @@ class SingleThreadTaskRunner;
 }
 
 namespace history {
-class CommitLaterTask;
 struct DownloadRow;
 class HistoryBackendClient;
 class HistoryBackendDBBaseTest;
@@ -480,7 +481,6 @@ 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 +828,10 @@ 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

[Marc Treib, 2017/02/02 12:59:24]

So IsCancelled()==true is the default state for an "empty" CancelableCallback?
That is a bit surprising to me; maybe worth a comment in the .cc where we depend
on that.

+  // can use Cancel() to cancel the scheduled commit. There can be only one
   // 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
@@ -890,6 +890,8 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   // List of observers
   base::ObserverList<HistoryBackendObserver> observers_;
 
+  base::WeakPtrFactory<HistoryBackend> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(HistoryBackend);
 };