Bug 836735 - Add interface to QI implementation for ProcessPriorityManager. r=bent

dom/ipc/ProcessPriorityManager.cpp

@@ -219,7 +219,8 @@ private:
   nsWeakPtr mMemoryMinimizerRunnable;
 };
 
-NS_IMPL_ISUPPORTS2(ProcessPriorityManager, nsIObserver, nsIDOMEventListener)
+NS_IMPL_ISUPPORTS3(ProcessPriorityManager, nsIObserver,
+                   nsIDOMEventListener, nsITimerCallback)
 
 ProcessPriorityManager::ProcessPriorityManager()
   : mProcessPriority(ProcessPriority(-1))