Bug 1251659, part 1 - test_bug967796.html should use SpecialPowers.pushPrefEnv. r=mrbkap

This should fix the intermittent e10s failure.

dom/events/test/mochitest.ini

@@ -135,7 +135,7 @@ skip-if = buildapp == 'b2g' # b2g(failing when the test gets moved around, and o
 [test_bug946632.html]
 skip-if = buildapp == 'b2g'
 [test_bug967796.html]
-skip-if = toolkit == "gonk" || e10s
+skip-if = toolkit == "gonk"
 [test_bug985988.html]
 [test_bug998809.html]
 [test_bug1017086_disable.html]

dom/events/test/test_bug967796.html

@@ -20,10 +20,13 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=967796
 
 /** Test for Bug 967796 **/
 
-SpecialPowers.setBoolPref("dom.w3c_pointer_events.enabled", true);      // Enable Pointer Events
-
 SimpleTest.waitForExplicitFinish();
-SimpleTest.waitForFocus(runTests);
+
+SpecialPowers.pushPrefEnv({"set": [["dom.w3c_pointer_events.enabled", true]]},
+  function() {
+    SimpleTest.waitForFocus(runTests);
+  });
+
 var outer;
 var middle;
 var inner;
@@ -161,8 +164,6 @@ function runTests() {
       elt.onpointerenter = null;
       elt.onpointerleave = null;
     });
-  SpecialPowers.clearUserPref("dom.w3c_pointer_events.enabled");      // Disable Pointer Events
-
   SimpleTest.finish();
 }