With the chromebook powered on (be careful), and your multimeter in DC volt mode, touch one probe to any metallic part of the computer chassis or any known ground (could even use the ground pin of the flash), then touch the other probe to the /WP pin (there was a datasheet sent out before with pictures of all of the different packages and their pinouts). If your meter reads 0V then the pin is being pulled down and the hardware /WP is being enforced. If it reads 1.8V or something around there then it might be a bad chip or something off in flashrom.