DetachFromSequence in Timer::Stop()

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 27 matching lines @@
 // 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().

[gab, 2017/06/01 16:29:49]

The documentation was already mentioning this as of
https://codereview.chromium.org/2491613004/

 
 #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 137 matching lines @@
   // The desired run time of |user_task_|. The user may update this at any time,
   // even if their previous request has not run yet. If |desired_run_time_| is
   // greater than |scheduled_run_time_|, a continuation task will be posted to
   // wait for the remaining time. This allows us to reuse the pending task so as
   // not to flood the delayed queues with orphaned tasks when the user code
   // excessively Stops and Starts the timer. This time can be a "zero" TimeTicks
   // if the task must be run immediately.
   TimeTicks desired_run_time_;
 
   // Timer isn't thread-safe and must only be used on its origin sequence
-  // (sequence on which it was started).
+  // (sequence on which it was started). Once fully Stop()'ed it may be
+  // destroyed or even restarted on another sequence.

[danakj, 2017/06/06 20:07:12]

s/even //

[gab, 2017/06/07 19:02:37]

Done.

   SequenceChecker origin_sequence_checker_;
 
   // Repeating timers automatically post the task again before calling the task
   // callback.
   const bool is_repeating_;
 
   // If true, hold on to the |user_task_| closure object for reuse.
   const bool retain_user_task_;
 
   // The tick clock used to calculate the run time for scheduled tasks.
@@ skipping 91 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_