Keymap for Alt keys on Chromebooks? [SOLVED]

I’m working on an app that uses Alt-Up and Alt-Down as keyboard commands, and CM’s built-in keymap works like a charm on Macs and Windows. On Chromebooks, however, pressing either key seems to trigger some other name. There seems to be some special handling required for Chromebook alt-key events. I don’t have a Chromebook to test on myself, but I’m wondering if anyone else has encountered this before? If so, what’s the keyname for the Alt key?

Nevermind: Chromebooks map Alt-Up and Alt-Down to PageUp and PageDown!