[Android] Refactor md5_check + add tests

build/android/gyp/dex.py

 #!/usr/bin/env python
 #
 # Copyright 2013 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 fnmatch
 import optparse
 import os
 import sys
 
 from util import build_utils
 from util import md5_check
 
 
 def DoDex(options, paths):
   dx_binary = os.path.join(options.android_sdk_root, 'platform-tools', 'dx')
   dex_cmd = [dx_binary, '--dex', '--output', options.dex_path] + paths
 
-  md5_stamp = '%s.md5' % options.dex_path
-  md5_checker = md5_check.Md5Checker(
-      stamp=md5_stamp, inputs=paths, command=dex_cmd)
-  if md5_checker.IsStale():
-    build_utils.CheckCallDie(dex_cmd, suppress_output=True)
-  else:
-    build_utils.Touch(options.dex_path)
-  md5_checker.Write()
+  record_path = '%s.md5.stamp' % options.dex_path
+  md5_check.CallAndRecordIfStale(
+      lambda: build_utils.CheckCallDie(dex_cmd, suppress_output=True),
+      record_path=record_path,
+      input_paths=paths,
+      input_strings=dex_cmd)
+
+  build_utils.Touch(options.dex_path)
 
 
 def main(argv):
   parser = optparse.OptionParser()
   parser.add_option('--android-sdk-root', help='Android sdk root directory.')
   parser.add_option('--dex-path', help='Dex output path.')
   parser.add_option('--stamp', help='Path to touch on success.')
 
   # TODO(newt): remove this once http://crbug.com/177552 is fixed in ninja.
   parser.add_option('--ignore', help='Ignored.')
 
   options, paths = parser.parse_args()
 
   DoDex(options, paths)
 
   if options.stamp:
     build_utils.Touch(options.stamp)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))