Revert of gpu: GPU service scheduler.

gpu/command_buffer/common/scheduling_priority.h

-// Copyright 2017 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 GPU_COMMAND_BUFFER_COMMON_SCHEDULING_PRIORITY_H_
-#define GPU_COMMAND_BUFFER_COMMON_SCHEDULING_PRIORITY_H_
-
-#include "gpu/gpu_export.h"
-
-namespace gpu {
-
-enum class SchedulingPriority {
-  // The Highest and High priorities can be used by priveleged clients only.
-  // This priority should be used for UI contexts.
-  kHighest,
-  // This priority is used by the scheduler for prioritizing contexts which have
-  // outstanding sync token waits.
-  kHigh,
-  // The following priorities can be used on unprivileged clients.
-  // This priority should be used as the default priority for all contexts.
-  kNormal,
-  kLow,
-  // This priority should be used for worker contexts.
-  kLowest,
-  kLast = kLowest
-};
-
-GPU_EXPORT const char* SchedulingPriorityToString(SchedulingPriority priority);
-
-}  // namespace gpu
-
-#endif  // GPU_COMMAND_BUFFER_COMMON_SCHEDULING_PRIORITY_H_