Test dynamic priorities

cc/raster/tile_task_runner.h

Index: cc/raster/tile_task_runner.h
diff --git a/cc/raster/tile_task_runner.h b/cc/raster/tile_task_runner.h
index ed0f29a701c3b696d1f9da44bd0b048196d1c9d3..55be94b5c7081e5cb139599abce839487e132f6e 100644
--- a/cc/raster/tile_task_runner.h
+++ b/cc/raster/tile_task_runner.h
@@ -34,7 +34,6 @@ class CC_EXPORT TileTaskClient {
 class CC_EXPORT TileTask : public Task {
  public:
   typedef std::vector<scoped_refptr<TileTask>> Vector;
-
   virtual void ScheduleOnOriginThread(TileTaskClient* client) = 0;
   virtual void CompleteOnOriginThread(TileTaskClient* client) = 0;
 
@@ -66,6 +65,7 @@ class CC_EXPORT ImageDecodeTask : public TileTask {
 class CC_EXPORT RasterTask : public TileTask {
  public:
   typedef std::vector<scoped_refptr<RasterTask>> Vector;
+  bool IsRasterTask() override { return true; }
 
   const ImageDecodeTask::Vector& dependencies() const { return dependencies_; }