Iran’s revolution has now run through a full cycle. A gruesomely captivating video of a young woman — laid out on a Tehran street after apparently being shot, blood pouring from her mouth and then across her face — swept Twitter, Facebook and other websites this weekend. The woman rapidly became a symbol of Iran’s escalating crisis, from a political confrontation to far more ominous physical clashes. Some sites refer to her as “Neda,” Farsi for the voice or the call. Tributes that incorporate startlingly upclose footage of her dyinghave started to spring up on YouTube.