Reland "[test] Fix cctest path separators on Windows"

test/message/testcfg.py

 # 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
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 34 matching lines @@
 
   def ListTests(self, context):
     tests = []
     for dirname, dirs, files in os.walk(self.root):
       for dotted in [x for x in dirs if x.startswith('.')]:
         dirs.remove(dotted)
       dirs.sort()
       files.sort()
       for filename in files:
         if filename.endswith(".js"):
-          testname = os.path.join(dirname[len(self.root) + 1:], filename[:-3])
+          fullpath = os.path.join(dirname, filename)
+          relpath = fullpath[len(self.root) + 1 : -3]
+          testname = relpath.replace(os.path.sep, "/")
           test = testcase.TestCase(self, testname)
           tests.append(test)
     return tests
 
   def GetFlagsForTestCase(self, testcase, context):
     source = self.GetSourceForTest(testcase)
     result = []
     flags_match = re.findall(FLAGS_PATTERN, source)
     for match in flags_match:
       result += match.strip().split()
@@ skipping 43 matching lines @@
       if not re.match(pattern, actual):
         return True
     return False
 
   def StripOutputForTransmit(self, testcase):
     pass
 
 
 def GetSuite(name, root):
   return MessageTestSuite(name, root)