[test] migrate mkgrokdump suite to TestLoader

R=machenbach@chromium.org
CC=yangguo@chromium.org,sergiyb@chromium.org

Bug: v8:8728
Change-Id: Ia45bd1f19f97c7c3491b57e6808f2c27643f5521
Reviewed-on: https://chromium-review.googlesource.com/c/1466561Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59528}

test/mkgrokdump/testcfg.py

@@ -13,7 +13,8 @@ SHELL = 'mkgrokdump'
 
 
 class TestLoader(testsuite.TestLoader):
-  pass
+  def _list_test_filenames(self):
+    yield SHELL
 
 #TODO(tmrts): refactor the test creation logic to migrate to TestLoader
 class TestSuite(testsuite.TestSuite):
@@ -23,10 +24,6 @@ class TestSuite(testsuite.TestSuite):
     v8_path = os.path.dirname(os.path.dirname(os.path.abspath(self.root)))
     self.expected_path = os.path.join(v8_path, 'tools', 'v8heapconst.py')
 
-  def ListTests(self):
-    test = self._test_loader._create_test(SHELL, self)
-    return [test]
-
   def _test_loader_class(self):
     return TestLoader