Henry says Jimmy wants to sit near a window to keep watch over whoever might be coming into the Diner parking lot. It's interesting that Jimmy doesn't bother to look over his own shoulder. For in this scene the internecine war is not between rival gangs but between extra and star. Here the leaders are "tailed" by the extra in the next booth over.
What tensions or struggles result from the strange proximity of this chomping extra? He listens and at the same time seems not to listen. He isn't tailing our two heroes but he does seem bored, like any person alone at a diner, and casually overhearing the conversation at the next table. His active jaws express all the anxiety that goes unarticulated by the main characters, who keep cool exteriors even as they assign executions and think about death. "He was jumpy. He hadn't touched a thing," observes Henry. The mobsters come to a diner but neither eat nor talk frankly. The extra behind De Niro does both at once: he eats frankly.
The extra eats, and in doing so gives this scene its real bite. When we get a freeze-frame of Jimmy's face, the blurry jowls of the man over his shoulder give the picture its ominous and unsettling quality.The extra embodies that thing about Jimmy that Henry cannot bring into focus, cannot pinpoint. As Jimmy conveys the details about the task, the extra chews as if he too were dispensing something rather than digesting something. The matter-of-factness of the extra is what De Niro (and his character, Jimmy) can only aspire to.
At the very beginning of the scene, Scorcese's signature tracking shot cuts through the crowd of the diner as if it were Moses parting the sea. In the clip above, a man at the counter gets up as if to leave but then quickly scoots forward in order to make room for Scorcese's dolly (the shot impedes his exit). Scorcese habitually demonstrates his tracking shot "mastery" by moving the camera through the busy back rooms crammed with people not in the limelight (the kitchen area of the fancy club in Goodfellas, for example). In the conversation at the booth, however, Scorcese's camera stops cutting through the extras and gets assaulted by one. This extra doesn't pretend to eat (like an actor) and doesn't pretend not to eat (the way De Niro does), he just eats. His eyes wearily search the room as if he were looking for a way to put his finger on the joy imparted by this presumably greasy food. The solipsism of the happy eater is well known. It says: this plate I look into is the center of my world; I couldn't care less about the acting going on the booth next to mine; I will even look into Scorcese's camera as I sit here and digest, thank you very much.
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