Bug 1659435 - disable browser_nested_iframe.js on mac x64 r=intermittent-reviewers,MasterWayZ DONTBUILD

Differential Revision: https://phabricator.services.mozilla.com/D137036

accessible/tests/browser/fission/browser.ini

@@ -9,6 +9,8 @@ support-files =
 [browser_hidden_iframe.js]
 https_first_disabled = true
 [browser_nested_iframe.js]
+skip-if =
+  os == 'mac' && bits == 64 && !debug # Bug 1659435
 [browser_reframe_root.js]
 [browser_reframe_visibility.js]
 [browser_src_change.js]