Fix diff generation by difflib to report missing end of file newlines.

Tools/Scripts/webkitpy/layout_tests/port/base_unittest.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #    * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #    * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 125 matching lines @@
             u'a\xac\u1234\u20ac\U00008000', 'act', 'exp.txt', 'act.txt')
 
         # And make sure we actually get diff output.
         diff = port.diff_text('foo', 'bar', 'exp.txt', 'act.txt')
         self.assertIn('foo', diff)
         self.assertIn('bar', diff)
         self.assertIn('exp.txt', diff)
         self.assertIn('act.txt', diff)
         self.assertNotIn('nosuchthing', diff)
 
+        # Test for missing newline at end of file diff output.
+        content_a = "Hello\n\nWorld"
+        content_b = "Hello\n\nWorld\n\n\n"
+        expected = "--- exp.txt\n+++ act.txt\n@@ -1,3 +1,5 @@\n Hello\n \n-World\n\ No newline at end of file\n+World\n+\n+\n"
+        self.assertEqual(expected, port.diff_text(content_a, content_b, 'exp.txt', 'act.txt'))
+
     def test_setup_test_run(self):
         port = self.make_port()
         # This routine is a no-op. We just test it for coverage.
         port.setup_test_run()
 
     def test_test_dirs(self):
         port = self.make_port()
         port.host.filesystem.write_text_file(port.layout_tests_dir() + '/canvas/test', '')
         port.host.filesystem.write_text_file(port.layout_tests_dir() + '/css2.1/test', '')
         dirs = port.test_dirs()
@@ skipping 305 matching lines @@
         suite = VirtualTestSuite('suite/bar', 'base/foo', ['--args'])
         self.assertFalse(hasattr(suite, 'name'))
         self.assertFalse(hasattr(suite, 'base'))
         self.assertFalse(hasattr(suite, 'args'))
 
     def test_legacy(self):
         suite = VirtualTestSuite('suite/bar', 'base/foo', ['--args'], use_legacy_naming=True)
         self.assertEqual(suite.name, 'virtual/suite/bar')
         self.assertEqual(suite.base, 'base/foo')
         self.assertEqual(suite.args, ['--args'])