Make marking a reftests as NeedsRebaseline/NeedsManualRebaseline a lint error.

Tools/Scripts/webkitpy/layout_tests/models/test_expectations.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 138 matching lines @@
         parsed_specifiers = set([specifier.lower() for specifier in expectation_line.specifiers])
         expectation_line.matching_configurations = self._test_configuration_converter.to_config_set(parsed_specifiers, expectation_line.warnings)
 
     def _lint_line(self, expectation_line):
         expectations = [expectation.lower() for expectation in expectation_line.expectations]
         if not expectation_line.bugs and self.WONTFIX_MODIFIER not in expectations:
             expectation_line.warnings.append(self.MISSING_BUG_WARNING)
         if self.REBASELINE_MODIFIER in expectations:
             expectation_line.warnings.append('REBASELINE should only be used for running rebaseline.py. Cannot be checked in.')
 
+        if self.NEEDS_REBASELINE_MODIFIER in expectations or self.NEEDS_MANUAL_REBASELINE_MODIFIER in expectations:
+            for test in expectation_line.matching_tests:
+                if self._port.reference_files(test):
+                    expectation_line.warnings.append('A reftest cannot be marked as NeedsRebaseline/NeedsManualRebaseline')
+
     def _parse_expectations(self, expectation_line):
         result = set()
         for part in expectation_line.expectations:
             expectation = TestExpectations.expectation_from_string(part)
             if expectation is None:  # Careful, PASS is currently 0.
                 expectation_line.warnings.append('Unsupported expectation: %s' % part)
                 continue
             result.add(expectation)
         expectation_line.parsed_expectations = result
 
@@ skipping 926 matching lines @@
             # If reconstitute_only_these is an empty list, we want to return original_string.
             # So we need to compare reconstitute_only_these to None, not just check if it's falsey.
             if reconstitute_only_these is None or expectation_line in reconstitute_only_these:
                 return expectation_line.to_string(test_configuration_converter)
             return expectation_line.original_string
 
         def nones_out(expectation_line):
             return expectation_line is not None
 
         return "\n".join(filter(nones_out, map(serialize, expectation_lines)))