cc: Add TaskGraphRunner sub-namespaces with task concurrency limits.

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 const int kDefaultSubNamespace = 0;
+  static const int kDefaultMaxConcurrentTasks = 16;
+
   static unsigned kBenchmarkTaskPriority;
   static unsigned kTaskSetFinishedTaskPriorityBase;
   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().
@@ skipping 18 matching lines @@
   // each task in |graph|.
   static void ScheduleTasksOnOriginThread(TileTaskClient* client,
                                           TaskGraph* graph);
 
   // Utility function that can be used to build a task graph. Inserts a node
   // that represents |task| in |graph|. See TaskGraph definition for valid
   // |priority| values.
   static void InsertNodeForTask(TaskGraph* graph,
                                 TileTask* task,
                                 unsigned priority,
-                                size_t dependencies);
+                                size_t dependencies,
+                                int sub_namespace,
+                                int max_concurrent_tasks);
 
   // Utility function that can be used to build a task graph. Inserts nodes that
   // represent |task| and all its image decode dependencies in |graph|.
   static void InsertNodesForRasterTask(
       TaskGraph* graph,
       RasterTask* task,
       const ImageDecodeTask::Vector& decode_tasks,
-      unsigned priority);
+      unsigned priority,
+      int sub_namespace,
+      int max_concurrent_tasks);
 
   // Utility function that will create a temporary bitmap and copy pixels to
   // |memory| when necessary.
   static void PlaybackToMemory(void* memory,
                                ResourceFormat format,
                                const gfx::Size& size,
                                int stride,
                                const RasterSource* raster_source,
                                const gfx::Rect& rect,
                                float scale);
 
   // Type-checking downcast routine.
   virtual TileTaskRunner* AsTileTaskRunner() = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_TILE_TASK_WORKER_POOL_H_