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/gtest-parallel-wrapper.py

@@ -81,6 +81,10 @@ def get_args_and_env():
   parser.add_argument('--isolated-script-test-chartjson-output', type=str,
                       default=None)
 
+  # No-sandbox is a Chromium-specific flag, ignore it.
+  # TODO(oprypin): Remove (bugs.webrtc.org/8115)
+  parser.add_argument('--no-sandbox', action='store_true', default=False)
+
   # We have to do this, since --isolated-script-test-output is passed as an
   # argument to the executable by the swarming scripts, and we want to pass it
   # to gtest-parallel instead.