Extract diff_text function out of the Port class.

third_party/WebKit/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 499 matching lines @@
                 result = self._filesystem.read_binary_file(native_diff_filename)
             else:
                 err_str = "Image diff returned an exit code of %s. See http://crbug.com/278596" % exit_code
         except OSError as error:
             err_str = 'error running image diff: %s' % error
         finally:
             self._filesystem.rmtree(str(tempdir))
 
         return (result, err_str or None)
 
-    def diff_text(self, expected_text, actual_text, expected_filename, actual_filename):
-        """Returns a string containing the diff of the two text strings
-        in 'unified diff' format.
-        """
-
-        # The filenames show up in the diff output, make sure they're
-        # raw bytes and not unicode, so that they don't trigger join()
-        # trying to decode the input.
-        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)
-
-        # 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 1234 matching lines @@
 
     def __init__(self, base, args, reference_args=None):
         self.name = base
         self.base = base
         self.args = args
         self.reference_args = args if reference_args is None else reference_args
         self.tests = set()
 
     def __repr__(self):
         return "PhysicalTestSuite('%s', '%s', %s, %s)" % (self.name, self.base, self.args, self.reference_args)