Bug 633566 - Prevent the timer to be eaten alive by the GC. r=bz a=tests

layout/reftests/backgrounds/delay-image-response.sjs

@@ -25,6 +25,12 @@ const IMAGE_DATA =
    0x49,  0x45,  0x4E,  0x44,  0xAE,  0x42,  0x60,  0x82,
   ];
 
+/**
+ * The timer is needed when a delay is set. We need it to be out of the method
+ * so it is not eaten alive by the GC.
+ */
+var timer;
+
 function handleRequest(request, response) {
   var query = {};
   request.queryString.split('&').forEach(function (val) {
@@ -40,16 +46,20 @@ function handleRequest(request, response) {
     stream.writeByteArray(IMAGE_DATA, IMAGE_DATA.length);
   }
 
-  if ("delay" in query) {
-    response.processAsync();
-    const nsITimer = Components.interfaces.nsITimer;
-
-    var timer = Components.classes["@mozilla.org/timer;1"].createInstance(nsITimer);
-    timer.initWithCallback(function() {
-      imageWrite();
-      response.finish();
-    }, query["delay"], nsITimer.TYPE_ONE_SHOT);
-  } else {
+  // If there is no delay, we write the image and leave.
+  if (!("delay" in query)) {
     imageWrite();
+    return;
   }
+
+  // If there is a delay, we create a timer which, when it fires, will write
+  // image and leave.
+  response.processAsync();
+  const nsITimer = Components.interfaces.nsITimer;
+
+  timer = Components.classes["@mozilla.org/timer;1"].createInstance(nsITimer);
+  timer.initWithCallback(function() {
+    imageWrite();
+    response.finish();
+  }, query["delay"], nsITimer.TYPE_ONE_SHOT);
 }