[Isolates] Make test.py ignore occasional Windows unlink() failures

tools/test.py

 #!/usr/bin/env python
 #
 # Copyright 2008 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
@@ skipping 484 matching lines @@
         sleep_time = MAX_SLEEP_TIME
   return (process, exit_code, timed_out)
 
 
 def PrintError(str):
   sys.stderr.write(str)
   sys.stderr.write('\n')
 
 
 def CheckedUnlink(name):
-  try:
-    os.unlink(name)
-  except OSError, e:
-    PrintError("os.unlink() " + str(e))
-
+  # On Windows, when run with -jN in parallel processes,
+  # OS often fails to unlink the temp file. Not sure why.
+  # Need to retry.
+  # Idea from https://bugs.webkit.org/attachment.cgi?id=75982&action=prettypatch
+  retry_count = 0
+  while retry_count < 30:
+    try:
+      os.unlink(name)
+      return
+    except OSError, e:
+      retry_count += 1;
+      time.sleep(retry_count * 0.1)
+  PrintError("os.unlink() " + str(e))
 
 def Execute(args, context, timeout=None):
   (fd_out, outname) = tempfile.mkstemp()
   (fd_err, errname) = tempfile.mkstemp()
   (process, exit_code, timed_out) = RunProcess(
     context,
     timeout,
     args = args,
     stdout = fd_out,
     stderr = fd_err,
@@ skipping 947 matching lines @@
     for entry in timed_tests[:20]:
       t = FormatTime(entry.duration)
       sys.stderr.write("%4i (%s) %s\n" % (index, t, entry.GetLabel()))
       index += 1
 
   return result
 
 
 if __name__ == '__main__':
   sys.exit(Main())