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

Tools/Scripts/webkitpy/layout_tests/port/base.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 508 matching lines @@
         def to_raw_bytes(string_value):
             if isinstance(string_value, unicode):
                 return string_value.encode('utf-8')
             return string_value
         expected_filename = to_raw_bytes(expected_filename)
         actual_filename = to_raw_bytes(actual_filename)
         diff = difflib.unified_diff(expected_text.splitlines(True),
                                     actual_text.splitlines(True),
                                     expected_filename,
                                     actual_filename)
-        return ''.join(diff)
+
+        # The diff generated by the difflib is incorrect if one of the files
+        # does not have a newline at the end of the file and it is present in
+        # the diff. Relevant Python issue: http://bugs.python.org/issue2142
+        def diff_fixup(diff):
+            for line in diff:
+                yield line
+                if not line.endswith('\n'):
+                    yield '\n\ No newline at end of file\n'
+
+        return ''.join(diff_fixup(diff))
 
     def driver_name(self):
         if self.get_option('driver_name'):
             return self.get_option('driver_name')
         return self.CONTENT_SHELL_NAME
 
     def expected_baselines_by_extension(self, test_name):
         """Returns a dict mapping baseline suffix to relative path for each baseline in
         a test. For reftests, it returns ".==" or ".!=" instead of the suffix."""
         # FIXME: The name similarity between this and expected_baselines() below, is unfortunate.
@@ skipping 1222 matching lines @@
 
 class PhysicalTestSuite(object):
     def __init__(self, base, args):
         self.name = base
         self.base = base
         self.args = args
         self.tests = set()
 
     def __repr__(self):
         return "PhysicalTestSuite('%s', '%s', %s)" % (self.name, self.base, self.args)