Exit if pngcrush has a bug

tools/resources/optimize-png-files.sh

Index: tools/resources/optimize-png-files.sh
diff --git a/tools/resources/optimize-png-files.sh b/tools/resources/optimize-png-files.sh
index d9347ee8122c46f5a030198592e0257135bda799..c7b37d73777cef59d3b2ec44d7983ea115b43946 100755
--- a/tools/resources/optimize-png-files.sh
+++ b/tools/resources/optimize-png-files.sh
@@ -381,6 +381,19 @@ function fail_if_not_installed {
   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=$(pngcrush -v | awk "/pngcrush 1.7./ {print \$3}")
+  local version_num=$(echo $version | sed "s/\.//g")
+  if [[ (1748 -lt $version_num && $version_num -lt 1773) ]] ; then

[msw, 2014/09/05 19:05:43]

How did you find this range? I'd like to be sure that 1.7.73 and onward does not
have this defect. Will Ubuntu 14.04 LTS users have a clear path to upgrade?
(should we instruct them that they'll need to build source from xyz, since
Ubuntu's package manager only grabs 1.7.65-0.1, and there don't seem to be other
prebuilt Linux binaries?)

+    echo "Your pngcrush ($version) has a bug that exists from " \
+         "1.7.49 to 1.7.72  (see crbug.com/404893 for details)."
+    echo "Please upgrade pngcrush and try again"
+    exit 1;
+  fi
+}
+
 function show_help {
   local program=$(basename $0)
   echo \
@@ -461,6 +474,8 @@ shift $(($OPTIND -1))
 
 # Make sure we have all necessary commands installed.
 install_if_not_installed pngcrush pngcrush
+exit_if_bad_pngcrush_version
+
 if [ $OPTIMIZE_LEVEL -ge 1 ]; then
   install_if_not_installed optipng optipng