A less wordy version of r85947 and r85948

chrome/installer/mac/keystone_install.sh

 #!/bin/bash -p
 
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # usage: keystone_install.sh update_dmg_mount_point
 #
 # Called by the Keystone system to update the installed application with a new
 # version from a disk image.
@@ skipping 45 matching lines @@
 export -n SHELLOPTS
 
 set -o pipefail
 shopt -s nullglob
 
 ME="$(basename "${0}")"
 readonly ME
 
 # Workaround for http://code.google.com/p/chromium/issues/detail?id=83180#c3
 # In bash 4.0, "declare VAR" no longer initializes VAR if not already set.
-GOOGLE_CHROME_UPDATER_DEBUG="${GOOGLE_CHROME_UPDATER_DEBUG:-}"
+: ${GOOGLE_CHROME_UPDATER_DEBUG:=}
 err() {
   local error="${1}"
 
   local id=
   if [[ -n "${GOOGLE_CHROME_UPDATER_DEBUG}" ]]; then
     id=": ${$} $(date "+%Y-%m-%d %H:%M:%S %z")"
   fi
 
   echo "${ME}${id}: ${error}" >& 2
 }
@@ skipping 1185 matching lines @@
 
 # Check "less than" instead of "not equal to" in case Keystone ever changes to
 # pass more arguments.
 if [[ ${#} -lt 1 ]]; then
   usage
   exit 2
 fi
 
 main "${@}"
 exit ${?}