Replace dump_json_test_results flag by isolated-script-test-output.

This is because it's the default flag used in the recipes to dump a json output.
This CL also fixes some python3 lint issues in mb.py.

Bug: webrtc:13594
Change-Id: I9275b5da0963f801d3191703c2eb72d90befb5d7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/248142
Reviewed-by: Christoffer Jansson <jansson@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Jeremy Leconte <jleconte@google.com>
Cr-Commit-Position: refs/heads/main@{#35986}
diff --git a/tools_webrtc/gtest_parallel_wrapper_test.py b/tools_webrtc/gtest_parallel_wrapper_test.py
index df317555..609052d 100755
--- a/tools_webrtc/gtest_parallel_wrapper_test.py
+++ b/tools_webrtc/gtest_parallel_wrapper_test.py
@@ -108,6 +108,12 @@
     self.assertEqual(result.output_dir, '/tmp/foo')
     self.assertEqual(result.test_artifacts_dir, None)
 
+  def testJsonTestResults(self):
+    result = gtest_parallel_wrapper.ParseArgs(
+        ['--isolated-script-test-output', '/tmp/foo', 'exec'])
+    expected = self._Expected(['--dump_json_test_results=/tmp/foo', 'exec'])
+    self.assertEqual(result.gtest_parallel_args, expected)
+
   def testShortArg(self):
     result = gtest_parallel_wrapper.ParseArgs(['-d', '/tmp/foo', 'exec'])
     expected = self._Expected(['--output_dir=/tmp/foo', 'exec'])
@@ -131,13 +137,14 @@
       result = gtest_parallel_wrapper.ParseArgs([
           'some_test', '--some_flag=some_value', '--another_flag',
           '--output_dir=' + output_dir, '--store-test-artifacts',
+          '--isolated-script-test-output=SOME_DIR',
           '--isolated-script-test-perf-output=SOME_OTHER_DIR', '--foo=bar',
           '--baz'
       ])
       expected_artifacts_dir = os.path.join(output_dir, 'test_artifacts')
       expected = self._Expected([
-          '--output_dir=' + output_dir, 'some_test', '--',
-          '--test_artifacts_dir=' + expected_artifacts_dir,
+          '--output_dir=' + output_dir, '--dump_json_test_results=SOME_DIR',
+          'some_test', '--', '--test_artifacts_dir=' + expected_artifacts_dir,
           '--some_flag=some_value', '--another_flag',
           '--isolated_script_test_perf_output=SOME_OTHER_DIR', '--foo=bar',
           '--baz'