cc: Change tile manager to have a raw ptr for the task runner.

cc/tiles/tile_manager.h

Index: cc/tiles/tile_manager.h
diff --git a/cc/tiles/tile_manager.h b/cc/tiles/tile_manager.h
index b1c5f3cce1659429dfe98751439af08fb9984ce1..834bac7f82086634aa2ecb7edf3b3d2494870b4e 100644
--- a/cc/tiles/tile_manager.h
+++ b/cc/tiles/tile_manager.h
@@ -96,7 +96,7 @@ RasterTaskCompletionStatsAsValue(const RasterTaskCompletionStats& stats);
 class CC_EXPORT TileManager {
  public:
   TileManager(TileManagerClient* client,
-              scoped_refptr<base::SequencedTaskRunner> task_runner,
+              base::SequencedTaskRunner* task_runner,
               size_t scheduled_raster_task_limit,
               bool use_partial_raster);
   virtual ~TileManager();
@@ -271,7 +271,7 @@ class CC_EXPORT TileManager {
   ScheduledTasksStateAsValue() const;
 
   TileManagerClient* client_;
-  scoped_refptr<base::SequencedTaskRunner> task_runner_;
+  base::SequencedTaskRunner* task_runner_;
   ResourcePool* resource_pool_;
   TileTaskManager* tile_task_manager_;
   GlobalStateThatImpactsTilePriority global_state_;