I installed ChrUbuntu on an Acer C7 Chromebook, and I am able to dual boot Ubuntu 12.04 and ChromeOS and to control which OS loads by default. I tried to edit the
/etc/default/grub file and did run
update-grub successfully but saw no effects. I was trying to enable a "dmesg" style verbose system loading screen instead of the quiet splash screen (during the Ubuntu boot). I suspect that GRUB is not the bootloader on the machine or is functioning as a fairly late secondary bootloader only on the Linux partition. I realize that the Chromebook is a fairly closed system tightly controlled by Google, but since it is Linux at heart people may know the answer.
I don't need the "dmesg" style verbose boot badly enough; but did became curious about the bootloading on this system.
P.S. Just to clarify, I was trying to enable the verbose loading screen on the Ubuntu boot on the machine.