Bug 1004167 - Enable browser_backButtonFitts.js on Linux

--HG--
extra : rebase_source : f3680198b0183afdfde4fab2d11e231ae66755d2

browser/base/content/test/general/browser.ini

@@ -137,7 +137,7 @@ skip-if = e10s # Bug 1101993 - times out for unknown reasons when run in the dir
 [browser_autocomplete_oldschool_wrap.js]
 [browser_autocomplete_tag_star_visibility.js]
 [browser_backButtonFitts.js]
-skip-if = os != "win" # The Fitts Law back button is only supported on Windows (bug 571454)
+skip-if = os == "mac" # The Fitt's Law back button is not supported on OS X
 [browser_beforeunload_duplicate_dialogs.js]
 skip-if = e10s # bug 967873 means permitUnload doesn't work in e10s mode
 [browser_blob-channelname.js]