[Metrics] Fix presubmit scripts to return an error code on failure.

tools/metrics/common/presubmit_util.py

 # 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.
 
 import os
 import sys
 import logging
 import shutil
 
 import diff_util
@@ skipping 29 matching lines @@
 
   # Save the original file content.
   logging.info('Loading %s...', os.path.relpath(xml_path))
   with open(xml_path, 'rb') as f:
     original_xml = f.read()
 
   # Check there are no CR ('\r') characters in the file.
   if '\r' in original_xml:
     logging.error('DOS-style line endings (CR characters) detected - these are '
                   'not allowed. Please run dos2unix %s', original_filename)
-    return 1
+    sys.exit(1)
 
   try:
     pretty = prettyFn(original_xml)
   except Error:
     logging.error('Aborting parsing due to fatal errors.')
-    return 1
+    sys.exit(1)
 
   if original_xml == pretty:
     logging.info('%s is correctly pretty-printed.', original_filename)
-    return 0
+    sys.exit(0)
   if presubmit:
     logging.error('%s is not formatted correctly; run %s to fix.',
                   original_filename, script_name)
-    return 1
+    sys.exit(1)
 
   # Prompt user to consent on the change.
   if not diff_util.PromptUserToAcceptDiff(
       original_xml, pretty, 'Is the new version acceptable?'):
     logging.error('Diff not accepted. Aborting.')
-    return 1
+    sys.exit(1)
 
   logging.info('Creating backup file: %s', backup_filename)
   shutil.move(xml_path, os.path.join(xml_dir, backup_filename))
 
   with open(xml_path, 'wb') as f:
     f.write(pretty)
   logging.info('Updated %s. Don\'t forget to add it to your changelist',
                xml_path)
-  return 0
+  sys.exit(0)