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

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

Index: third_party/WebKit/Source/platform/scheduler/child/worker_scheduler.h
diff --git a/third_party/WebKit/Source/platform/scheduler/child/worker_scheduler.h b/third_party/WebKit/Source/platform/scheduler/child/worker_scheduler.h
index 5fc53ec067042b450e4ca95a8970bd522282d78c..a8bb2c59dd82b9cbd5680cf7769f0eaac3fde023 100644
--- a/third_party/WebKit/Source/platform/scheduler/child/worker_scheduler.h
+++ b/third_party/WebKit/Source/platform/scheduler/child/worker_scheduler.h
@@ -9,6 +9,7 @@
 
 #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"
@@ -23,6 +24,10 @@ class BLINK_PLATFORM_EXPORT WorkerScheduler : public ChildScheduler {
   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;
+
   // 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;