I think you have to ask.

Depending on crew, the self-serve snack cart may or may not be setup.

Got to love the consistency in crews.

Back in Nov 2007, the last time I did SFO-NRT in C, the snack cart was NOT setup, and I had to ask. Upon walking to the galley, my inquiry was addressed and hot noodles, small ham and cheese sandwiches, and Ghirardelli chocolates were offered.