Do not inherit TaskPriority in TaskTraits.

base/task_scheduler/task_traits.cc

 // 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.
 
 #include "base/task_scheduler/task_traits.h"
 
 #include <stddef.h>
 
 #include <ostream>
 
 #include "base/logging.h"
 #include "base/task_scheduler/scoped_set_task_priority_for_current_thread.h"
 
 namespace base {
 
 // Do not rely on defaults hard-coded below beyond the guarantees described in
 // the header; anything else is subject to change. Tasks should explicitly
 // request defaults if the behavior is critical to the task.
 TaskTraits::TaskTraits()
     : may_block_(false),
       with_base_sync_primitives_(false),
+      priority_set_explicitly_(false),

[gab, 2017/04/25 17:16:41]

Should be set to true in .WithPriority()?

[fdoray, 2017/04/25 17:57:48]

Sorry bad merge.

       priority_(internal::GetTaskPriorityForCurrentThread()),

[gab, 2017/04/25 17:16:41]

This doesn't match CL desc.

[fdoray, 2017/04/25 17:57:48]

Sorry bad merge.

       shutdown_behavior_(TaskShutdownBehavior::SKIP_ON_SHUTDOWN) {}

[gab, 2017/04/25 17:16:41]

Use inline member initialization in header for all traits

[fdoray, 2017/04/25 17:57:48]

We have to choose between initialization in header of bitfield.
http://stackoverflow.com/questions/29286203/default-values-for-bit-fields-in-c11

I'm leaning towards bitfield since member initialization won't be needed with
constexpr constructor (all members will be initialized with a call to a template
function in the constructor https://codereview.chromium.org/2829083002/) 

[gab, 2017/04/25 18:01:21]

Fast-access matters more than bit savings IMO (i.e. extra codegen to extract bit
is undesired).

Member initialization OTOH is about readability IMO and I prefer that.

 
 TaskTraits::~TaskTraits() = default;
 
 TaskTraits& TaskTraits::MayBlock() {
   may_block_ = true;
   return *this;
 }
 
 TaskTraits& TaskTraits::WithBaseSyncPrimitives() {
   with_base_sync_primitives_ = true;
@@ skipping 43 matching lines @@
   return os;
 }
 
 std::ostream& operator<<(std::ostream& os,
                          const TaskShutdownBehavior& shutdown_behavior) {
   os << TaskShutdownBehaviorToString(shutdown_behavior);
   return os;
 }
 
 }  // namespace base