Revert of Use TaskScheduler instead of WorkerPool in gbm_surfaceless.cc.

ui/ozone/platform/drm/gpu/gbm_surfaceless.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 "ui/ozone/platform/drm/gpu/gbm_surfaceless.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
-#include "base/task_scheduler/post_task.h"
+#include "base/threading/worker_pool.h"
 #include "base/trace_event/trace_event.h"
 #include "ui/ozone/common/egl_util.h"
 #include "ui/ozone/platform/drm/gpu/drm_vsync_provider.h"
 #include "ui/ozone/platform/drm/gpu/drm_window_proxy.h"
 #include "ui/ozone/platform/drm/gpu/gbm_surface_factory.h"
 #include "ui/ozone/platform/drm/gpu/scanout_buffer.h"
 
 namespace ui {
 
 namespace {
@@ skipping 101 matching lines @@
       return;
     }
 
     base::Closure fence_wait_task =
         base::Bind(&WaitForFence, GetDisplay(), fence);
 
     base::Closure fence_retired_callback =
         base::Bind(&GbmSurfaceless::FenceRetired, weak_factory_.GetWeakPtr(),
                    fence, frame);
 
-    base::PostTaskWithTraitsAndReply(
-        FROM_HERE, base::TaskTraits()
-                       .WithShutdownBehavior(
-                           base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN)
-                       .MayBlock(),
-        fence_wait_task, fence_retired_callback);
+    base::WorkerPool::PostTaskAndReply(FROM_HERE, fence_wait_task,
+                                       fence_retired_callback, false);
     return;  // Defer frame submission until fence signals.
   }
 
   frame->ready = true;
   SubmitFrame();
 }
 
 void GbmSurfaceless::PostSubBufferAsync(
     int x,
     int y,
@@ skipping 95 matching lines @@
   }
 
   SubmitFrame();
 }
 
 bool GbmSurfaceless::IsUniversalDisplayLinkDevice() {
   return planes_.empty() ? false : planes_[0].buffer->RequiresGlFinish();
 }
 
 }  // namespace ui