Disable the intermittently-failing tests (bug 536603) for Mac only, which is where they're failing.

--HG--
extra : transplant_source : %E2%F1%F2%3A%86%C7%C57%7F%16B%16m%94%0D%D6%EDg%A7r

layout/style/test/test_css_cross_domain.html

@@ -91,7 +91,10 @@ function check_iframe(ifr) {
 
 SimpleTest.waitForExplicitFinish();
 window.onload = function() {
-    check_iframe(document.getElementById("quirks"));
+    // The quirks-mode tests are inexplicably failing intermittently
+    // on Mac (bug 536603), so disable them for now.
+    if (navigator.platform.substring(0,3) != "Mac")
+        check_iframe(document.getElementById("quirks"));
     check_iframe(document.getElementById("standards"));
     SimpleTest.finish();
 };