It seems like a new entity's been added with the PeTI DLC.

In \instances\p2editor\global_pti_ents, there's a playtest_manager entity that doesn't have an image assigned to it (just the pink and black checkerboard). It's named @playtest and has inputs for StartRecording and StopRecording (not listed in the drop-down menu) though I'm not sure exactly what it's recording. It's not capable of outputting anything. You also can't select it from the entity list in the New Objects toolbar.

My apologies if this entity isn't new. I didn't see anything about it on the VDC so I'm assuming it's been recently added.

It's something that was implemented in an early beta. It was used to automatically record demo's (.dem files) but it was really buggy and valve decided to remove it from the final product.