Ensure .mk files aren't included in the tab character check.

presubmit_canned_checks.py

 # Copyright (c) 2012 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.
 
 """Generic presubmit checks that can be reused by other presubmit checks."""
 
 
 ### Description checks
 
 def CheckChangeHasTestField(input_api, output_api):
@@ skipping 253 matching lines @@
 
 def CheckChangeHasNoTabs(input_api, output_api, source_file_filter=None):
   """Checks that there are no tab characters in any of the text files to be
   submitted.
   """
   # In addition to the filter, make sure that makefiles are blacklisted.
   if not source_file_filter:
     # It's the default filter.
     source_file_filter = input_api.FilterSourceFile
   def filter_more(affected_file):
-    return (not input_api.os_path.basename(affected_file.LocalPath()) in
-                ('Makefile', 'makefile') and
+    basename = input_api.os_path.basename(affected_file.LocalPath())
+    return (not (basename in ('Makefile', 'makefile') or
+                 basename.endswith('.mk')) and
             source_file_filter(affected_file))
 
   tabs = _FindNewViolationsOfRule(lambda _, line : '\t' not in line,
                                   input_api, filter_more)
 
   if tabs:
     return [output_api.PresubmitPromptWarning('Found a tab character in:',
                                               long_text='\n'.join(tabs))]
   return []
 
@@ skipping 651 matching lines @@
     results.extend(input_api.canned_checks.CheckSvnForCommonMimeTypes(
         input_api, output_api))
     snapshot("checking license")
     results.extend(input_api.canned_checks.CheckLicense(
         input_api, output_api, license_header, source_file_filter=sources))
     snapshot("checking was uploaded")
     results.extend(input_api.canned_checks.CheckChangeWasUploaded(
         input_api, output_api))
   snapshot("done")
   return results