Bug 846067 - Add a missing interface to the QI impl. r=jlebar

--HG--
extra : rebase_source : 3f2d51ba19092cb85a1f481bdfe75a8a5d2dbd9e

dom/ipc/ProcessPriorityManager.cpp

@@ -218,7 +218,10 @@ private:
   nsWeakPtr mMemoryMinimizerRunnable;
 };
 
-NS_IMPL_ISUPPORTS2(ProcessPriorityManager, nsIObserver, nsIDOMEventListener)
+NS_IMPL_ISUPPORTS3(ProcessPriorityManager,
+                   nsIObserver,
+                   nsIDOMEventListener,
+                   nsITimerCallback)
 
 ProcessPriorityManager::ProcessPriorityManager()
   : mHoldsCPUWakeLock(false)