Bug 1441712 - Avoid unnecessary calls to generateQI in Timer.jsm r=florian

MozReview-Commit-ID: AMe6L3OHH6x

--HG--
extra : rebase_source : ed21b92b7e4013b523bb046543a4c497b961fddb

toolkit/modules/Timer.jsm

@@ -18,6 +18,9 @@ var gNextId = 1; // setTimeout and setInterval must return a positive integer
 
 var gTimerTable = new Map(); // int -> nsITimer
 
+// Don't generate this for every timer.
+var setTimeout_timerCallbackQI = XPCOMUtils.generateQI([Ci.nsITimerCallback, Ci.nsINamed]);
+
 function _setTimeoutOrIsInterval(aCallback, aMilliseconds, aIsInterval,
                                  aTarget, aArgs) {
   if (typeof aCallback !== "function") {
@@ -31,8 +34,7 @@ function _setTimeoutOrIsInterval(aCallback, aMilliseconds, aIsInterval,
   }
 
   let callback = {
-    QueryInterface: XPCOMUtils.generateQI([Ci.nsITimerCallback,
-                                           Ci.nsINamed]),
+    QueryInterface: setTimeout_timerCallbackQI,
 
     // nsITimerCallback
     notify() {