Add a PRESUBMIT check for broken .ico files.

tools/resources/optimize-ico-files.py

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """Windows ICO file crusher.
 
 Optimizes the PNG images within a Windows ICO icon file. This extracts all of
 the sub-images within the file, runs any PNG-formatted images through
 optimize-png-files.sh, then packs them back into an ICO file.
@@ skipping 14 matching lines @@
 
 def main(args=None):
   if args is None:
     args = sys.argv[1:]
 
   parser = argparse.ArgumentParser(description='Crush Windows ICO files.')
   parser.add_argument('files', metavar='ICO', type=argparse.FileType('r+b'),
                       nargs='+', help='.ico files to be crushed')
   parser.add_argument('-o', dest='optimization_level', metavar='OPT', type=int,
                       help='optimization level')
+  parser.add_argument('--lint', dest='lint', action='store_true',
+                      help='test the ICO file without modifying (set status '
+                      'to 1 on error)')
   parser.add_argument('-d', '--debug', dest='debug', action='store_true',
                       help='enable debug logging')
 
   args = parser.parse_args()
 
   if args.debug:
     logging.getLogger().setLevel(logging.DEBUG)
 
+  failed = False
   for file in args.files:
     buf = StringIO.StringIO()
     file.seek(0, os.SEEK_END)
     old_length = file.tell()
     file.seek(0, os.SEEK_SET)
+
+    if args.lint:
+      for error in ico_tools.LintIcoFile(file):
+        logging.warning('%s: %s', file.name, error)
+        # Any errors should cause this process to exit with a status of 1.
+        failed = True
+      continue
+
     ico_tools.OptimizeIcoFile(file, buf, args.optimization_level)
 
     new_length = len(buf.getvalue())
 
     # Always write (even if file size not reduced), because we make other fixes
     # such as regenerating the AND mask.
     file.truncate(new_length)
     file.seek(0)
     file.write(buf.getvalue())
 
     if new_length >= old_length:
       logging.info('%s : Could not reduce file size.', file.name)
     else:
       saving = old_length - new_length
       saving_percent = float(saving) / old_length
       logging.info('%s : %d => %d (%d bytes : %d %%)', file.name, old_length,
                    new_length, saving, int(saving_percent * 100))
 
+  return failed
+
 if __name__ == '__main__':
   sys.exit(main())