Install png optimization commands for optimization levels >= 1

tools/resources/optimize-png-files.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.
 
 # The optimization code is based on pngslim (http://goo.gl/a0XHg)
 # and executes a similar pipleline to optimize the png file size.
 # The steps that require pngoptimizercl/pngrewrite/deflopt are omitted,
 # but this runs all other processes, including:
 # 1) various color-dependent optimizations using optipng.
@@ skipping 373 matching lines @@
       OPTIMIZE_LEVEL=$OPTARG
       [ "$1" == "-o" ] && shift
       shift;;
     [h?])
       show_help;;
   esac
 done
 
 # Make sure we have all necessary commands installed.
 install_if_not_installed pngcrush pngcrush
-if [ $OPTIMIZE_LEVEL == 2 ]; then
+if [ $OPTIMIZE_LEVEL -ge 1 ]; then
   install_if_not_installed optipng optipng
 
   if $using_cygwin ; then
     fail_if_not_installed advdef "http://advancemame.sourceforge.net/comp-readme.html"
   else
     install_if_not_installed advdef advancecomp
   fi
 
   if $using_cygwin ; then
     pngout_url="http://www.advsys.net/ken/utils.htm"
@@ skipping 32 matching lines @@
        "that could be optimized" \
        "in $(date -u -d @$SECONDS +%T)s"
 else
   let diff=$TOTAL_OLD_BYTES-$TOTAL_NEW_BYTES
   let percent=$diff*100/$TOTAL_OLD_BYTES
   echo "Processed $PROCESSED_FILE files (out of $TOTAL_FILE files)" \
        "in $(date -u -d @$SECONDS +%T)s"
   echo "Result : $TOTAL_OLD_BYTES => $TOTAL_NEW_BYTES bytes" \
        "($diff bytes : $percent %)"
 fi