Fix leak in debug mirror cache.

tools/generate-runtime-tests.py

 #!/usr/bin/env python
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import itertools
 import js2c
 import multiprocessing
 import optparse
 import os
@@ skipping 33 matching lines @@
 # TYPED_ARRAYS_CHECK_RUNTIME_FUNCTION
 
 # Counts of functions in each detection state. These are used to assert
 # that the parser doesn't bit-rot. Change the values as needed when you add,
 # remove or change runtime functions, but make sure we don't lose our ability
 # to parse them!
 EXPECTED_FUNCTION_COUNT = 358
 EXPECTED_FUZZABLE_COUNT = 325
 EXPECTED_CCTEST_COUNT = 6
 EXPECTED_UNKNOWN_COUNT = 5
-EXPECTED_BUILTINS_COUNT = 781
+EXPECTED_BUILTINS_COUNT = 782
 
 
 # Don't call these at all.
 BLACKLISTED = [
   "Abort",  # Kills the process.
   "AbortJS",  # Kills the process.
   "CompileForOnStackReplacement",  # Riddled with ASSERTs.
   "IS_VAR",  # Not implemented in the runtime.
   "ListNatives",  # Not available in Release mode.
   "SetAllocationTimeout",  # Too slow for fuzzing.
@@ skipping 1241 matching lines @@
       for i in range(len(processes)):
         processes[i].join()
     except KeyboardInterrupt:
       stop_running.set()
       for i in range(len(processes)):
         processes[i].join()
     return 0
 
 if __name__ == "__main__":
   sys.exit(Main())