Expose Timer::AbandonAndStop, so it can safely be destroyed on another thread.

base/timer/timer.h

 // 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.
 
 // OneShotTimer and RepeatingTimer provide a simple timer API.  As the names
 // suggest, OneShotTimer calls you back once after a time delay expires.
 // RepeatingTimer on the other hand calls you back periodically with the
 // prescribed time interval.
 //
 // OneShotTimer and RepeatingTimer both cancel the timer when they go out of
@@ skipping 23 matching lines @@
 //
 // Both OneShotTimer and RepeatingTimer also support a Reset method, which
 // allows you to easily defer the timer event until the timer delay passes once
 // again.  So, in the above example, if 0.5 seconds have already passed,
 // calling Reset on |timer_| would postpone DoStuff by another 1 second.  In
 // other words, Reset is shorthand for calling Stop and then Start again with
 // the same arguments.
 //
 // These APIs are not thread safe. All methods must be called from the same
 // sequence (not necessarily the construction sequence), except for the
-// destructor and SetTaskRunner() which may be called from any sequence when the
-// timer is not running (i.e. when Start() has never been called or Stop() has
-// been called since the last Start()). By default, the scheduled tasks will be
-// run on the same sequence that the Timer was *started on*, but this can be
-// changed *prior* to Start() via SetTaskRunner().
+// destructor and SetTaskRunner().
+// - The destructor may be called from any sequence when the timer is not
+// running and there is no scheduled task active, i.e. when Start() has never
+// been called or after AbandonAndStop() has been called.
+// - SetTaskRunner() may be called from any sequence when the timer is not
+// running, i.e. when Start() has never been called or Stop() has been called
+// since the last Start().
+//
+// By default, the scheduled tasks will be run on the same sequence that the
+// Timer was *started on*, but this can be changed *prior* to Start() via
+// SetTaskRunner().
 
 #ifndef BASE_TIMER_TIMER_H_
 #define BASE_TIMER_TIMER_H_
 
 // IMPORTANT: If you change timer code, make sure that all tests (including
 // disabled ones) from timer_unittests.cc pass locally. Some are disabled
 // because they're flaky on the buildbot, but when you run them locally you
 // should be able to tell the difference.
 
 #include <memory>
@@ skipping 60 matching lines @@
   // Start the timer to run at the given |delay| from now. If the timer is
   // already running, it will be replaced to call the given |user_task|.
   virtual void Start(const tracked_objects::Location& posted_from,
                      TimeDelta delay,
                      const base::Closure& user_task);
 
   // Call this method to stop and cancel the timer.  It is a no-op if the timer
   // is not running.
   virtual void Stop();
 
+  // Stop running task (if any) and abandon scheduled task (if any).
+  void AbandonAndStop() {
+    AbandonScheduledTask();
+
+    Stop();
+    // No more member accesses here: |this| could be deleted at this point.
+  }
+
   // Call this method to reset the timer delay. The |user_task_| must be set. If
   // the timer is not running, this will start it by posting a task.
   virtual void Reset();
 
   const base::Closure& user_task() const { return user_task_; }
   const TimeTicks& desired_run_time() const { return desired_run_time_; }
 
  protected:
   // Returns the current tick count.
   TimeTicks Now() const;
@@ skipping 20 matching lines @@
   // sequence is returned.
   scoped_refptr<SequencedTaskRunner> GetTaskRunner();
 
   // Disable |scheduled_task_| and abandon it so that it no longer refers back
   // to this object.
   void AbandonScheduledTask();
 
   // Called by BaseTimerTaskInternal when the delayed task fires.
   void RunScheduledTask();
 
-  // Stop running task (if any) and abandon scheduled task (if any).
-  void AbandonAndStop() {
-    AbandonScheduledTask();
-
-    Stop();
-    // No more member accesses here: |this| could be deleted at this point.
-  }
-
   // When non-null, the |scheduled_task_| was posted to call RunScheduledTask()
   // at |scheduled_run_time_|.
   BaseTimerTaskInternal* scheduled_task_;
 
   // The task runner on which the task should be scheduled. If it is null, the
   // task runner for the current sequence will be used.
   scoped_refptr<SequencedTaskRunner> task_runner_;
 
   // Location in user code.
   tracked_objects::Location posted_from_;
@@ skipping 122 matching lines @@
 // to link in MSVC. But clang-plugin does not allow inline definitions of
 // virtual methods, so the inline definition lives in the header file here
 // to satisfy both.
 inline void DelayTimer::Reset() {
   Timer::Reset();
 }
 
 }  // namespace base
 
 #endif  // BASE_TIMER_TIMER_H_