Bug 1200498 - Clean up dom/browser-element mochitest.ini that has skip-if toolkit != gtk2 now that gtk3 is the default

dom/browser-element/mochitest/priority/mochitest.ini

@@ -1,6 +1,6 @@
 [DEFAULT]
 # Good luck running these tests on anything but desktop Linux.
-skip-if = toolkit != "gtk2" || ((buildapp =='mulet' || buildapp == 'b2g') && (toolkit != 'gonk' || debug)) || e10s
+run-if = os == 'linux' && buildapp == 'browser' && !e10s
 
 # Note: ../browserElementTestHelpers.js makes all tests in this directory OOP,
 # because testing the process-priority manager without OOP frames does not make