Update from https://crrev.com/309415

cc/resources/tile_task_worker_pool.h

 // Copyright 2013 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 CC_RESOURCES_TILE_TASK_WORKER_POOL_H_
 #define CC_RESOURCES_TILE_TASK_WORKER_POOL_H_
 
+#include "base/threading/platform_thread.h"
 #include "cc/resources/tile_task_runner.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace base {
 class SequencedTaskRunner;
 }
 
 namespace cc {
 class RasterSource;
 class RenderingStatsInstrumentation;
 
 class CC_EXPORT TileTaskWorkerPool {
  public:
   static unsigned kBenchmarkTaskPriority;
   static unsigned kTaskSetFinishedTaskPriority;
   static unsigned kTileTaskPriorityBase;
 
   TileTaskWorkerPool();
   virtual ~TileTaskWorkerPool();
 
   // Set the number of threads to use for the global TaskGraphRunner instance.
   // This can only be called once and must be called prior to
   // GetNumWorkerThreads().
   static void SetNumWorkerThreads(int num_threads);
 
   // Returns the number of threads used for the global TaskGraphRunner instance.
   static int GetNumWorkerThreads();
 
+  // Set the priority of worker threads.
+  static void SetWorkerThreadPriority(base::ThreadPriority priority);
+
   // Returns a pointer to the global TaskGraphRunner instance.
   static TaskGraphRunner* GetTaskGraphRunner();
 
   // Utility function that can be used to create a "Task set finished" task that
   // posts |callback| to |task_runner| when run.
   static scoped_refptr<TileTask> CreateTaskSetFinishedTask(
       base::SequencedTaskRunner* task_runner,
       const base::Closure& callback);
 
   // Utility function that can be used to call ::ScheduleOnOriginThread() for
@@ skipping 27 matching lines @@
                                const gfx::Rect& rect,
                                float scale);
 
   // Type-checking downcast routine.
   virtual TileTaskRunner* AsTileTaskRunner() = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_TILE_TASK_WORKER_POOL_H_