[NOT COMMITTED] Inline TaskTraits' destructor per it only having POD type members

base/task_scheduler/task_traits.h

 // Copyright 2016 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.
 
 #ifndef BASE_TASK_SCHEDULER_TASK_TRAITS_H_
 #define BASE_TASK_SCHEDULER_TASK_TRAITS_H_
 
 #include <stdint.h>
 
 #include <iosfwd>
@@ skipping 69 matching lines @@
  public:
   // Constructs a default TaskTraits for tasks with
   //     (1) no I/O,
   //     (2) low priority, and
   //     (3) may block shutdown or be skipped on shutdown.
   // Tasks that require stricter guarantees should highlight those by requesting
   // explicit traits below.
   TaskTraits();
   TaskTraits(const TaskTraits& other) = default;
   TaskTraits& operator=(const TaskTraits& other) = default;
-  ~TaskTraits();
+  ~TaskTraits() = default;

[robliao, 2016/04/07 17:43:18]

The Chromium guidance is

"Define them in the implementation file unless you really need them to be
inlined."

Also noted, this also apparently breaks forward declared variables (presumably
since the compiler now needs to know everything about setting the object up). 

https://www.chromium.org/developers/coding-style/cpp-dos-and-donts#TOC-Stop-i...

Having said that, do we gain something from inlining this destructor?

[gab, 2016/04/08 21:00:04]

Hmm, interesting, do we expect TaskTraits to be fwd-declared much?
If it's not inlined then SchedulerParallelTaskRunner also has to have an
explicit out-of-line destructor:
https://codereview.chromium.org/1708773002/diff/550001/base/task_scheduler/sc...

(that review is why I wondered whether TaskTraits had a trivial inline
destructor with POD types only)

But I guess the point of that style rule is that having that dependency on
SchedulerParallelTaskRunner is no good anyways (probably doesn't matter much in
that case since all callers won't inline but rather use virtual dispatch to get
to the destructor but wtv).

So I guess not inlining is the right thing here after all.

Closing, thanks.

[gab, 2016/04/08 21:01:48]

Actually that destructor is private so virtual dispatch is really the only way
to get to it and inlining isn't a concern, so nothing needs to change, ignore me
:-)!

 
   // Allows tasks with these traits to do file I/O.
   TaskTraits& WithFileIO();
 
   // Applies |priority| to tasks with these traits.
   TaskTraits& WithPriority(TaskPriority priority);
 
   // Applies |shutdown_behavior| to tasks with these traits.
   TaskTraits& WithShutdownBehavior(TaskShutdownBehavior shutdown_behavior);
 
@@ skipping 30 matching lines @@
 BASE_EXPORT std::ostream& operator<<(std::ostream& os,
                                      const TaskPriority& shutdown_behavior);
 
 BASE_EXPORT std::ostream& operator<<(
     std::ostream& os,
     const TaskShutdownBehavior& shutdown_behavior);
 
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_TRAITS_H_