Bug 1549875 - disable browser_mouseButtonVariation on Linux_64_opt for frequent failures. r=intermittent-reviewers,bhearsum DONTBUILD

Differential Revision: https://phabricator.services.mozilla.com/D117625

toolkit/components/pictureinpicture/tests/browser.ini

@@ -51,7 +51,9 @@ skip-if = (os == "mac" && debug) || os == "linux" #Bug 1566173, Bug 1664667
 support-files = 
   test-page-with-nan-video-duration.html
 [browser_mouseButtonVariation.js]
-skip-if = debug
+skip-if =
+  debug
+  os == 'linux' && bits == 64 && !debug # Bug 1549875
 [browser_noToggleOnAudio.js]
 [browser_playerControls.js]
 [browser_preserveTabPipIconOverlay.js]