gpu: GPU service scheduler.

gpu/command_buffer/common/gpu_stream_constants.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 GPU_IPC_COMMON_GPU_STREAM_CONSTANTS_H_
 #define GPU_IPC_COMMON_GPU_STREAM_CONSTANTS_H_
 
+#include "gpu/gpu_export.h"
+
 namespace gpu {
 
-enum class GpuStreamPriority { REAL_TIME, HIGH, NORMAL, LOW, LAST = LOW };
+enum class GpuStreamPriority : int { REAL_TIME, HIGH, NORMAL, LOW, LAST = LOW };
+static const int kNumGpuStreamPriorities = 4;
 
-enum GpuStreamId { GPU_STREAM_DEFAULT = -1, GPU_STREAM_INVALID = 0 };
+enum GpuStreamId {
+  GPU_STREAM_INVALID = -1,
+  GPU_STREAM_DEFAULT = 0,
+  GPU_STREAM_WORKER = 1,
+};
+
+GPU_EXPORT const char* GpuStreamPriorityToString(GpuStreamPriority priority);
 
 }  // namespace gpu
 
 #endif  // GPU_IPC_COMMON_GPU_STREAM_CONSTANTS_H_