Allow chronos user to renice back to 0

src/scripts/customize_rootfs.sh

 #!/bin/bash
 
 # Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Script to customize the root file system after packages have been installed.
 #
 # NOTE: This script should be called by build_image.sh. Do not run this
 # on your own unless you know what you are doing.
@@ skipping 66 matching lines @@
     "${ROOT_FS_DIR}"/etc/group
 done
 
 sudo mkdir -p "${ROOT_FS_DIR}/home/${ADD_USER}"
 sudo chown 1000.1000 "${ROOT_FS_DIR}/home/${ADD_USER}"
 cat <<EOF | sudo dd of="${ROOT_FS_DIR}/etc/sudoers" conv=notrunc oflag=append
 %adm ALL=(ALL) ALL
 $ADD_USER ALL=(ALL) ALL
 EOF
 sudo chmod 0440 "${ROOT_FS_DIR}/etc/sudoers"
+echo "# Allow chronos user to renice processes so that chrome will adjust tab priorities" | \
+  sudo dd of="${ROOT_FS_DIR}/etc/security/limits.conf" conv=notrunc oflag=append
+echo "chronos hard nice 0" | \
+  sudo dd of="${ROOT_FS_DIR}/etc/security/limits.conf" conv=notrunc oflag=append
 
 # Set CHROMEOS_VERSION_DESCRIPTION here (uses vars set in chromeos_version.sh)
 # Was removed from chromeos_version.sh which can also be run outside of chroot
 # where CHROMEOS_REVISION is set
 # We have to set (in build_image.sh) and use REAL_USER due to many nested
 # chroots which lose $USER state.
 . "${SCRIPTS_DIR}/chromeos_version.sh"
 if [ ${CHROMEOS_OFFICIAL:-0} = 1 ]; then
   export CHROMEOS_VERSION_DESCRIPTION="${CHROMEOS_VERSION_STRING} (Official Build ${CHROMEOS_REVISION:?})"
 elif [ "$REAL_USER" = "chrome-bot" ]
@@ skipping 149 matching lines @@
 cat <<EOF | sudo dd of="${ROOT_FS_DIR}/etc/network/interfaces"
 auto lo
 iface lo inet loopback
 EOF
 
 cat <<EOF | sudo dd of="${ROOT_FS_DIR}/etc/resolv.conf"
 # Use the connman dns proxy.
 nameserver 127.0.0.1
 EOF
 sudo chmod a-wx "${ROOT_FS_DIR}/etc/resolv.conf"