Add a note about false positives on "copyright" word into licenses checker

android_webview/tools/copyright_scanner.py

 # Copyright 2014 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.
 
 """Utilities for scanning source files to determine code authorship.
 """
 
 import itertools
 
 def ForwardSlashesToOsPathSeps(input_api, path):
@@ skipping 358 matching lines @@
     # deleted, the scanner will not complain.
     files_to_check |= whitelisted_files | deleted_files
 
   (unknown_files, missing_files, stale_files) = _DoScanAtPresubmit(
     input_api, list(whitelisted_files), list(files_to_check))
   results = []
   if unknown_files:
     results.append(output_api.PresubmitError(
         'The following files contain a third-party license but are not in ' \
         'a listed third-party directory and are not whitelisted. You must ' \
-        'add the following files to the whitelist file ' \
-        '%s:' % _GetWhitelistFileName(input_api),
+        'add the following files to the whitelist file %s\n' \
+        '(Note that if the code you are adding does not actually contain ' \
+        'any third-party code, it may contain the word "copyright", which ' \
+        'should be masked out, e.g. by writing it as "copy-right"):' \
+        '' % _GetWhitelistFileName(input_api),
         sorted(unknown_files)))
   if missing_files:
     results.append(output_api.PresubmitPromptWarning(
         'The following files are whitelisted in %s, ' \
         'but do not exist or not files:' % _GetWhitelistFileName(input_api),
         sorted(missing_files)))
   if stale_files:
     results.append(output_api.PresubmitPromptWarning(
         'The following files are whitelisted unnecessarily. You must ' \
         'remove the following files from the whitelist file ' \
         '%s:' % _GetWhitelistFileName(input_api),
         sorted(stale_files)))
   return results