[test] Key variant flags by variant name everywhere.

test/preparser/testcfg.py

 # Copyright 2011 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 108 matching lines @@
       result.append(os.path.join(self.root, testcase.path + ".js"))
       return testcase.flags + result
     return testcase.flags
 
   def GetSourceForTest(self, testcase):
     if testcase.flags[0] == "-e":
       return testcase.flags[1]
     with open(testcase.flags[0]) as f:
       return f.read()
 
-  def VariantFlags(self, testcase, default_flags):
-    return [[]];
+  def _VariantGeneratorFactory(self):
+    return testsuite.StandardVariantGenerator
 
 
 def GetSuite(name, root):
   return PreparserTestSuite(name, root)