Update TaskScheduler docs to make it more obvious how a TaskScheduler should be put in place.

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 109 matching lines @@
   // base::Create(Sequenced|SingleTreaded)TaskRunnerWithTraits(). If a thread is
   // really needed, make it non-joinable and add cleanup work at the end of the
   // thread's main function (if using base::Thread, override Cleanup()).
   //
   // On Windows, join processes asynchronously using base::win::ObjectWatcher.
   //
   // MayBlock() must be specified in conjunction with this trait if and only if
   // removing usage of methods listed above in the labeled tasks would still
   // result in tasks that may block (per MayBlock()'s definition).
   //
-  // In doubt, consult with base/task_scheduler/OWNERS.
+  // In doubt, consult with //base/task_scheduler/OWNERS.
   TaskTraits& WithBaseSyncPrimitives();
 
   // Applies |priority| to tasks with these traits.
   TaskTraits& WithPriority(TaskPriority priority);
 
   // Applies |shutdown_behavior| to tasks with these traits.
   TaskTraits& WithShutdownBehavior(TaskShutdownBehavior shutdown_behavior);
 
   // Returns true if tasks with these traits may block.
   bool may_block() const { return may_block_; }
@@ skipping 24 matching lines @@
 // DCHECK and EXPECT statements.
 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_