Cycles: Expose passes size to device tasks

This is needed so devices can know the size of a tile buffer before any
tiles are acquired.

intern/cycles/device/device_task.h

@@ -51,6 +51,8 @@ public:
 	int shader_filter;
 	int shader_x, shader_w;
 
+	int passes_size;
+
 	explicit DeviceTask(Type type = PATH_TRACE);
 
 	int get_subtask_count(int num, int max_size = 0);

intern/cycles/render/session.cpp

@@ -887,6 +887,7 @@ void Session::path_trace()
 	task.need_finish_queue = params.progressive_refine;
 	task.integrator_branched = scene->integrator->method == Integrator::BRANCHED_PATH;
 	task.requested_tile_size = params.tile_size;
+	task.passes_size = tile_manager.params.get_passes_size();
 
 	device->task_add(task);
 }