Bug 1389086 Part2: Use once event listeners to avoid they are triggered after the test is done. r=smaug.

MozReview-Commit-ID: JrYXWs2yhSO

dom/events/test/pointerevents/mochitest.ini

@@ -14,7 +14,6 @@ support-files =
 [test_bug1303704.html]
 [test_bug1315862.html]
 [test_bug1323158.html]
-  disabled = disabled # Bug 1389086 - Intermittent failures
 [test_empty_file.html]
   disabled = disabled # Bug 1150091 - Issue with support-files
 [test_pointerevent_attributes_hoverable_pointers-manual.html]

dom/events/test/pointerevents/test_bug1323158.html

@@ -43,7 +43,7 @@ function runTests() {
   pointerBoundaryEvents.forEach((event) => {
     target1.addEventListener(event, (e) => {
       receivedPointerBoundaryEvents[event] = e;
-    });
+    }, {once: true});
   });
 
   let attributes = ["target", "relatedTarget"];
@@ -59,7 +59,7 @@ function runTests() {
         });
       }
       receivedPointerBoundaryEvents[mouseEvent2pointerEvent[event]] = null;
-    });
+    }, {once: true});
   });
   target0.addEventListener("pointerdown", (e) => {
     target1.setPointerCapture(e.pointerId);