In 3.8:

chromeos/config/armel/common.config:CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
chromeos/config/i386/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/x86_64/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set

In 3.10:

chromeos/config/armel/common.config:CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
chromeos/config/i386/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/x86_64/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set

In 3.14:

dianders@tictac:v3.14 ((54c97f93cccb...))$ git grep 'CONFIG_BOOTPARAM_HARDLOCKUP_PANIC[^_]' chromeos
chromeos/config/arm64/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/armel/chromiumos-arm.flavour.config:CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
chromeos/config/armel/chromiumos-ipq806x.flavour.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/armel/chromiumos-rockchip.flavour.config:CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
chromeos/config/i386/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/mips/common.config:CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
chromeos/config/x86_64/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set

In 3.18:

chromeos/config/arm64/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/armel/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/i386/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/mips/chromiumos-mipsel.flavour.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set
chromeos/config/x86_64/common.config:# CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set