Fix cr-bash-helpers for Mac w/ Homebrew, which doesn't have realpath.

tools/cr/cr-bash-helpers.sh

 #!/bin/bash
 
 # Copyright 2013 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.
 
 # Source this file into your shell to gain the cr function and tab completion
 # for it
 
 # Make sure we're being sourced (possibly by another script). Check for bash
 # since zsh sets $0 when sourcing.
 if [[ -n "$BASH_VERSION" && "${BASH_SOURCE:-$0}" == "$0" ]]; then
   echo "ERROR: cr-bash-helpers.sh must be sourced."
   exit 1
 fi
 
+READLINK_e="readlink -e"
+if [[ -x `which greadlink` ]]; then
+  READLINK_e="greadlink -e"
+fi
 
-cr_base_dir=$(dirname $(realpath "${BASH_SOURCE:-$0}"))
+cr_base_dir=$(dirname $($READLINK_e "${BASH_SOURCE:-$0}"))
 cr_main="${cr_base_dir}/main.py"
 cr_exec=("PYTHONDONTWRITEBYTECODE=1" "python" "${cr_main}")
 
 # The main entry point to the cr tool.
 # Invokes the python script with pyc files turned off.
 function cr() {
   env ${cr_exec[@]} "$@"
 }
 
 # Attempts to cd to the root/src of the current client.
@@ skipping 12 matching lines @@
   local cur="${COMP_WORDS[COMP_CWORD]}"
   local main="python -B "${cr_main}")"
   local completions="$(env COMP_CWORD=${COMP_CWORD} \
       COMP_WORD=${cur} \
       ${cr_exec[@]})"
   COMPREPLY=( $(compgen -W "${completions}" -- ${cur}) )
 }
 
 # Setup the bash auto complete
 complete -F _cr_complete cr