Stop silently accepting unsupported flags in test binaries

Instead explicitly ignore only the flags we know should be ignored.

BUG=webrtc:7568

Review-Url: https://codereview.webrtc.org/2968003003
Cr-Commit-Position: refs/heads/master@{#19412}

tools_webrtc/valgrind/webrtc_tests.py

@@ -24,6 +24,7 @@ Chrome's suppression files and our own, so we can easily maintain WebRTC
 specific suppressions in our own files.
 """
 
+import argparse
 import logging
 import optparse
 import os
@@ -124,6 +125,15 @@ def main(_):
                     help="run the tests with --test-launcher-shard-index")
   options, args = parser.parse_args()
 
+  ignore_parser = argparse.ArgumentParser()
+  # Ignore Chromium-specific flags
+  # TODO(oprypin): Remove (bugs.webrtc.org/8115)
+  ignore_parser.add_argument('--isolated-script-test-output',
+                             type=str, default=None)
+  ignore_parser.add_argument('--isolated-script-test-chartjson-output',
+                             type=str, default=None)
+  _, args = ignore_parser.parse_known_args(args)
+
   if options.verbose:
     logging_utils.config_root(logging.DEBUG)
   else: