Fix RebaselineTest._copy_existing_baseline() to not assume that fallback directory names match port…

Tools/Scripts/webkitpy/tool/commands/rebaseline.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 98 matching lines @@
             baseline_search_path = port.baseline_search_path()
             try:
                 index = baseline_search_path.index(path_to_rebaseline)
                 if index:
                     immediate_predecessors_in_fallback.append(self._tool.filesystem.basename(baseline_search_path[index - 1]))
             except ValueError:
                 # index throw's a ValueError if the item isn't in the list.
                 pass
         return immediate_predecessors_in_fallback
 
+    def _port_for_primary_baseline(self, baseline):
+        for port in [self._tool.port_factory.get(port_name) for port_name in self._tool.port_factory.all_port_names()]:
+            if self._tool.filesystem.basename(port.baseline_version_dir()) == baseline:
+                return port
+        raise Exception("Failed to find port for primary baseline %s." % baseline)
+
     def _copy_existing_baseline(self, move_overwritten_baselines_to, test_name, suffix):
         old_baselines = []
         new_baselines = []
 
         # Need to gather all the baseline paths before modifying the filesystem since
         # the modifications can affect the results of port.expected_filename.
-        for platform in move_overwritten_baselines_to:
-            port = self._tool.port_factory.get(platform)
+        for port in [self._port_for_primary_baseline(baseline) for baseline in move_overwritten_baselines_to]:
             old_baseline = port.expected_filename(test_name, "." + suffix)
             if not self._tool.filesystem.exists(old_baseline):
                 _log.debug("No existing baseline for %s." % test_name)
                 continue
 
             new_baseline = self._tool.filesystem.join(port.baseline_path(), self._file_name_for_expected_result(test_name, suffix))
             if self._tool.filesystem.exists(new_baseline):
                 _log.debug("Existing baseline at %s, not copying over it." % new_baseline)
                 continue
 
@@ skipping 367 matching lines @@
             tests = args or self._tests_to_update(builder)
             for test in tests:
                 if test not in test_prefix_list:
                     test_prefix_list[test] = {}
                 test_prefix_list[test][builder.name()] = suffixes_to_update
 
         if options.verbose:
             _log.debug("rebaseline-json: " + str(test_prefix_list))
 
         self._rebaseline(options, test_prefix_list)