Add script to apply a patch from rietveld.

tests/patch_test.py

 #!/usr/bin/env python
 # Copyright (c) 2011 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.
 
 """Unit tests for patch.py."""
 
 import os
 import sys
 import unittest
@@ skipping 174 matching lines @@
     self.assertEquals(c.patchlevel, 1)
     self.assertEquals(c.get(), diff)
 
   def testFilePatchBadDiff(self):
     try:
       patch.FilePatchDiff('foo', 'data', [])
       self.fail()
     except patch.UnsupportedPatchFormat:
       pass
 
+  def testFilePatchNoDiff(self):
+    try:
+      patch.FilePatchDiff('foo', '', [])
+      self.fail()
+    except patch.UnsupportedPatchFormat:
+      pass
+
+  def testFilePatchNoneDiff(self):
+    try:
+      patch.FilePatchDiff('foo', None, [])
+      self.fail()
+    except patch.UnsupportedPatchFormat:
+      pass
+
   def testFilePatchBadDiffName(self):
     try:
       patch.FilePatchDiff('foo', SVN_PATCH, [])
       self.fail()
     except patch.UnsupportedPatchFormat:
       pass
 
   def testInvalidFilePatchDiffGit(self):
     try:
       patch.FilePatchDiff('svn_utils_test.txt', (
@@ skipping 142 matching lines @@
     patch.FilePatchDiff(
         'chrome/browser/chromeos/views/webui_menu_widget.h',
         GIT_RENAME_PARTIAL, [])
     patch.FilePatchDiff('pp', GIT_COPY, [])
     patch.FilePatchDiff('foo', GIT_NEW, [])
     self.assertTrue(True)
 
 
 if __name__ == '__main__':
   unittest.main()