[wpt] Update Marionette executor to use "--remote-allow-system-access" argument for Firefox.

Differential Revision: https://phabricator.services.mozilla.com/D241411

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1710425
gecko-commit: c765284053d2d43d86f0cb197d0e55a1ca41bcb6
gecko-reviewers: Sasha

Author: whimboo

Diff for: tools/wptrunner/wptrunner/browsers/firefox.py

@@ -377,7 +377,8 @@ def start(self):
                           self.e10s)
 
         args = self.binary_args[:] if self.binary_args else []
-        args += [cmd_arg("marionette"), "about:blank"]
+        args += [cmd_arg("marionette"),
+                 cmd_arg("remote-allow-system-access"), "about:blank"]
 
         debug_args, cmd = browser_command(self.binary,
                                           args,

Diff for: tools/wptrunner/wptrunner/browsers/firefox_android.py

@@ -280,10 +280,12 @@ def start(self, **kwargs):
 
         self.leak_report_file = None
 
-        debug_args, cmd = browser_command(self.package_name,
-                                          self.binary_args if self.binary_args else [] +
-                                          [cmd_arg("marionette"), "about:blank"],
-                                          self.debug_info)
+        args = self.binary_args[:] if self.binary_args else []
+        args += [cmd_arg("marionette"),
+                 cmd_arg("remote-allow-system-access"), "about:blank"]
+
+        debug_args, cmd = browser_command(
+            self.package_name, args, self.debug_info)
 
         env = get_environ(self.chaos_mode_flags, self.env_extras)