[scheduler] Remove blink::scheduler::TaskQueue from public API.

third_party/WebKit/Source/platform/scheduler/child/worker_scheduler.h

 // Copyright 2015 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 THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WORKER_SCHEDULER_H_
 #define THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WORKER_SCHEDULER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
+#include "platform/scheduler/base/task_queue.h"
 #include "public/platform/WebCommon.h"
 #include "public/platform/scheduler/child/child_scheduler.h"
 #include "public/platform/scheduler/child/single_thread_idle_task_runner.h"
 
 namespace blink {
 namespace scheduler {
 class SchedulerTqmDelegate;
 
 class BLINK_PLATFORM_EXPORT WorkerScheduler : public ChildScheduler {
  public:
   ~WorkerScheduler() override;
   static std::unique_ptr<WorkerScheduler> Create(
       scoped_refptr<SchedulerTqmDelegate> main_task_runner);
 
+  // Blink should use WorkerScheduler::DefaultTaskQueue instead of
+  // ChildScheduler::DefaultTaskRunner.
+  virtual scoped_refptr<TaskQueue> DefaultTaskQueue() = 0;

[Sami, 2017/04/12 16:45:21]

Hmm, why?-) And how do we make sure someone doesn't get this wrong?

[altimin, 2017/04/12 17:02:25]

They're essentially the same, TaskQueue is a subclass of SingleThreadTaskRunner.
TaskQueue exposes more blink-specific methods and there are a lot of places in
blink where task queue is expected. This is pretty impossible to get wrong
(compiler will enforce it)

And scheduler->DefaultTaskQueue()->PostTask and
scheduler->DefaultTaskRunner()->PostTask do exactly the same thing.

+
   // Must be called before the scheduler can be used. Does any post construction
   // initialization needed such as initializing idle period detection.
   virtual void Init() = 0;
 
  protected:
   WorkerScheduler();
   DISALLOW_COPY_AND_ASSIGN(WorkerScheduler);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WORKER_SCHEDULER_H_