I can also confirm that setting GRUB_CMDLINE_LINUX_DEFAULT="tpm_tis.force=1" and running sudo update-grub fixed this problem on an Acer C720 Chromebook, running the default kernel that installs with Ubuntu 14.04.
I can also confirm that setting GRUB_CMDLINE_ LINUX_DEFAULT= "tpm_tis. force=1" and running sudo update-grub fixed this problem on an Acer C720 Chromebook, running the default kernel that installs with Ubuntu 14.04.