Revert of Refactor History's CommitLaterTask with CancelableCallback

components/history/core/browser/history_backend.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/history/core/browser/history_backend.h"
 
 #include <algorithm>
 #include <functional>
 #include <list>
 #include <map>
@@ skipping 96 matching lines @@
   } else {
     mv.redirects = redirects;
     if (mv.redirects.back() != mv.url) {
       // The last url must be the target url.
       mv.redirects.push_back(mv.url);
     }
   }
   return mv;
 }
 
+// This task is run on a timer so that commits happen at regular intervals
+// so they are batched together. The important thing about this class is that
+// it supports canceling of the task so the reference to the backend will be
+// freed. The problem is that when history is shutting down, there is likely
+// to be one of these commits still pending and holding a reference.
+//
+// The backend can call Cancel to have this task release the reference. The
+// task will still run (if we ever get to processing the event before
+// shutdown), but it will not do anything.
+//
+// Note that this is a refcounted object and is not a task in itself. It should
+// be assigned to a RunnableMethod.
+//
+// TODO(brettw): bug 1165182: This should be replaced with a
+// base::WeakPtrFactory which will handle everything automatically (like we do
+// in ExpireHistoryBackend).
+class CommitLaterTask : public base::RefCounted<CommitLaterTask> {
+ public:
+  explicit CommitLaterTask(HistoryBackend* history_backend)
+      : history_backend_(history_backend) {}
+
+  // The backend will call this function if it is being destroyed so that we
+  // release our reference.
+  void Cancel() { history_backend_ = nullptr; }
+
+  void RunCommit() {
+    if (history_backend_)
+      history_backend_->Commit();
+  }
+
+ private:
+  friend class base::RefCounted<CommitLaterTask>;
+
+  ~CommitLaterTask() {}
+
+  scoped_refptr<HistoryBackend> history_backend_;
+};
+
 QueuedHistoryDBTask::QueuedHistoryDBTask(
     std::unique_ptr<HistoryDBTask> task,
     scoped_refptr<base::SingleThreadTaskRunner> origin_loop,
     const base::CancelableTaskTracker::IsCanceledCallback& is_canceled)
     : task_(std::move(task)),
       origin_loop_(origin_loop),
       is_canceled_(is_canceled) {
   DCHECK(task_);
   DCHECK(origin_loop_);
   DCHECK(!is_canceled_.is_null());
@@ skipping 45 matching lines @@
     scoped_refptr<base::SequencedTaskRunner> task_runner)
     : delegate_(delegate),
       scheduled_kill_db_(false),
       expirer_(this, backend_client.get(), task_runner),
       recent_redirects_(kMaxRedirectCount),
       segment_queried_(false),
       backend_client_(std::move(backend_client)),
       task_runner_(task_runner) {}
 
 HistoryBackend::~HistoryBackend() {
-  DCHECK(scheduled_commit_.IsCancelled()) << "Deleting without cleanup";
+  DCHECK(!scheduled_commit_) << "Deleting without cleanup";
   queued_history_db_tasks_.clear();
 
   // Release stashed embedder object before cleaning up the databases.
   supports_user_data_helper_.reset();
 
   // First close the databases before optionally running the "destroy" task.
   CloseAllDatabases();
 
   if (!backend_destroy_task_.is_null()) {
     // Notify an interested party (typically a unit test) that we're done.
@@ skipping 2004 matching lines @@
 
   if (thumbnail_db_) {
     thumbnail_db_->CommitTransaction();
     DCHECK_EQ(thumbnail_db_->transaction_nesting(), 0)
         << "Somebody left a transaction open";
     thumbnail_db_->BeginTransaction();
   }
 }
 
 void HistoryBackend::ScheduleCommit() {
-  // Non-cancelled means there's an already scheduled commit. Note that
-  // CancelableClosure starts cancelled with the default constructor.
-  if (!scheduled_commit_.IsCancelled())
+  if (scheduled_commit_)
     return;
-
-  scheduled_commit_.Reset(
-      base::Bind(&HistoryBackend::Commit, base::Unretained(this)));
-
+  scheduled_commit_ = new CommitLaterTask(this);
   task_runner_->PostDelayedTask(
-      FROM_HERE, scheduled_commit_.callback(),
+      FROM_HERE,
+      base::Bind(&CommitLaterTask::RunCommit, scheduled_commit_),
       base::TimeDelta::FromSeconds(kCommitIntervalSeconds));
 }
 
 void HistoryBackend::CancelScheduledCommit() {
-  scheduled_commit_.Cancel();
+  if (scheduled_commit_) {
+    scheduled_commit_->Cancel();
+    scheduled_commit_ = nullptr;
+  }
 }
 
 void HistoryBackend::ProcessDBTaskImpl() {
   if (!db_) {
     // db went away, release all the refs.
     queued_history_db_tasks_.clear();
     return;
   }
 
   // Remove any canceled tasks.
@@ skipping 377 matching lines @@
   // transaction is currently open.
   db_->CommitTransaction();
   db_->Vacuum();
   db_->BeginTransaction();
   db_->GetStartDate(&first_recorded_time_);
 
   return true;
 }
 
 }  // namespace history