Do not inherit TaskPriority in TaskTraits.

base/task_scheduler/post_task.cc

Index: base/task_scheduler/post_task.cc
diff --git a/base/task_scheduler/post_task.cc b/base/task_scheduler/post_task.cc
index 6f9adae27f4cc3312928d773a522058761e7ea32..6abe2134d1bdd315d8f6480ad9699c61cc0330fb 100644
--- a/base/task_scheduler/post_task.cc
+++ b/base/task_scheduler/post_task.cc
@@ -7,6 +7,7 @@
 #include <utility>
 
 #include "base/logging.h"
+#include "base/task_scheduler/scoped_set_task_priority_for_current_thread.h"
 #include "base/task_scheduler/task_scheduler.h"
 #include "base/threading/post_task_and_reply_impl.h"
 
@@ -14,6 +15,15 @@ namespace base {
 
 namespace {
 
+TaskTraits SetExplicitPriorityInTaskTraits(const TaskTraits& traits) {

[gab, 2017/04/25 14:19:16]

This doesn't "set" a priority, it returns a new one based on |traits|.

[fdoray, 2017/04/25 15:21:18]

Done.

+  TaskTraits traits_with_explicit_priority(traits);
+  if (traits.priority() == TaskPriority::INHERITED) {
+    traits_with_explicit_priority.WithPriority(
+        internal::GetTaskPriorityForCurrentThread());
+  }
+  return traits_with_explicit_priority;

[gab, 2017/04/25 14:19:16]

How about this whole function as:

return traits.priority() == TaskPriority::INHERITED
    ? traits.WithPriority(internal::GetTaskPriorityForCurrentThread())
    : traits;

this avoids one copy in both cases I think.

[fdoray, 2017/04/25 15:21:18]

Done. A copy is required to call WithPriority() (cannot be called on const
TaskTraits).

+}
+
 class PostTaskAndReplyTaskRunner : public internal::PostTaskAndReplyImpl {
  public:
   explicit PostTaskAndReplyTaskRunner(const TaskTraits& traits)
@@ -62,7 +72,8 @@ void PostDelayedTaskWithTraits(const tracked_objects::Location& from_here,
   DCHECK(TaskScheduler::GetInstance())
       << "Ref. Prerequisite section of post_task.h";
   TaskScheduler::GetInstance()->PostDelayedTaskWithTraits(
-      from_here, traits, std::move(task), std::move(delay));
+      from_here, SetExplicitPriorityInTaskTraits(traits), std::move(task),
+      std::move(delay));
 }
 
 void PostTaskWithTraitsAndReply(const tracked_objects::Location& from_here,
@@ -76,7 +87,8 @@ void PostTaskWithTraitsAndReply(const tracked_objects::Location& from_here,
 scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(const TaskTraits& traits) {
   DCHECK(TaskScheduler::GetInstance())
       << "Ref. Prerequisite section of post_task.h";
-  return TaskScheduler::GetInstance()->CreateTaskRunnerWithTraits(traits);
+  return TaskScheduler::GetInstance()->CreateTaskRunnerWithTraits(
+      SetExplicitPriorityInTaskTraits(traits));
 }
 
 scoped_refptr<SequencedTaskRunner> CreateSequencedTaskRunnerWithTraits(
@@ -84,7 +96,7 @@ scoped_refptr<SequencedTaskRunner> CreateSequencedTaskRunnerWithTraits(
   DCHECK(TaskScheduler::GetInstance())
       << "Ref. Prerequisite section of post_task.h";
   return TaskScheduler::GetInstance()->CreateSequencedTaskRunnerWithTraits(
-      traits);
+      SetExplicitPriorityInTaskTraits(traits));
 }
 
 scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunnerWithTraits(
@@ -92,7 +104,7 @@ scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunnerWithTraits(
   DCHECK(TaskScheduler::GetInstance())
       << "Ref. Prerequisite section of post_task.h";
   return TaskScheduler::GetInstance()->CreateSingleThreadTaskRunnerWithTraits(
-      traits);
+      SetExplicitPriorityInTaskTraits(traits));
 }
 
 #if defined(OS_WIN)
@@ -100,7 +112,8 @@ scoped_refptr<SingleThreadTaskRunner> CreateCOMSTATaskRunnerWithTraits(
     const TaskTraits& traits) {
   DCHECK(TaskScheduler::GetInstance())
       << "Ref. Prerequisite section of post_task.h";
-  return TaskScheduler::GetInstance()->CreateCOMSTATaskRunnerWithTraits(traits);
+  return TaskScheduler::GetInstance()->CreateCOMSTATaskRunnerWithTraits(
+      SetExplicitPriorityInTaskTraits(traits));
 }
 #endif  // defined(OS_WIN)