Fix test driver json output.

tools/testrunner/local/progress.py

 # Copyright 2012 the V8 project authors. 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 in the documentation and/or other materials provided
@@ skipping 315 matching lines @@
     self.results.append({
       "name": test.GetLabel(),
       "flags": test.flags,
       "command": EscapeCommand(self.runner.GetCommand(test)).replace(
           ABS_PATH_PREFIX, ""),
       "run": test.run,
       "stdout": test.output.stdout,
       "stderr": test.output.stderr,
       "exit_code": test.output.exit_code,
       "result": test.suite.GetOutcome(test),
-      "expected": list(test.outcomes) or ["PASS"],
+      "expected": list(test.outcomes or ["PASS"]),
     })
 
 
 PROGRESS_INDICATORS = {
   'verbose': VerboseProgressIndicator,
   'dots': DotsProgressIndicator,
   'color': ColorProgressIndicator,
   'mono': MonochromeProgressIndicator
 }