Pngcrush version determined correctly.

tools/resources/optimize-png-files.sh

 #!/bin/bash -i
 # 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 366 matching lines @@
   which $program > /dev/null 2>&1
   if [ $? != 0 ]; then
     echo "Couldn't find $program. Please download and install it from $url ."
     exit 1
   fi
 }
 
 # Check pngcrush version and exit if the version is in bad range.
 # See crbug.com/404893.
 function exit_if_bad_pngcrush_version {
-  local version=$(pngcrush -v | awk "/pngcrush 1.7./ {print \$3}")
+  local version=$(pngcrush -v 2>&1 | awk "/pngcrush 1.7./ {print \$3}")
   local version_num=$(echo $version | sed "s/\.//g")
   if [[ (1748 -lt $version_num && $version_num -lt 1773) ]] ; then
     echo "Your pngcrush ($version) has a bug that exists from " \
          "1.7.49 to 1.7.72  (see crbug.com/404893 for details)."
     echo "Please upgrade pngcrush and try again"
     exit 1;
   fi
 }
 
 function show_help {
@@ skipping 141 matching lines @@
 if [ $PROCESSED_FILE != 0 ]; then
   let diff=$TOTAL_OLD_BYTES-$TOTAL_NEW_BYTES
   let percent=$diff*100/$TOTAL_OLD_BYTES
   echo "Result: $TOTAL_OLD_BYTES => $TOTAL_NEW_BYTES bytes" \
        "($diff bytes: $percent%)"
 fi
 if [ $CORRUPTED_FILE != 0 ]; then
   echo "Warning: corrupted files found: $CORRUPTED_FILE"
   echo "Please contact the author of the CL that landed corrupted png files"
 fi