--- a/layout/xul/nsRepeatService.cpp
+++ b/layout/xul/nsRepeatService.cpp
@@ -48,17 +48,17 @@ void nsRepeatService::Start(Callback aCa
   NS_PRECONDITION(aCallback != nullptr, "null ptr");
 
   mCallback = aCallback;
   mCallbackData = aCallbackData;
   nsresult rv;
   mRepeatTimer = do_CreateInstance("@mozilla.org/timer;1", &rv);
 
   if (NS_SUCCEEDED(rv))  {
-    mRepeatTimer->InitWithCallback(this, aInitialDelay, nsITimer::TYPE_ONE_SHOT);
+    InitTimerCallback(aInitialDelay);
   }
 }
 
 void nsRepeatService::Stop(Callback aCallback, void* aCallbackData)
 {
   if (mCallback != aCallback || mCallbackData != aCallbackData)
     return;
 
@@ -73,15 +73,21 @@ void nsRepeatService::Stop(Callback aCal
 
 NS_IMETHODIMP nsRepeatService::Notify(nsITimer *timer)
 {
   // do callback
   if (mCallback)
     mCallback(mCallbackData);
 
   // start timer again.
-  if (mRepeatTimer) {
-    mRepeatTimer->InitWithCallback(this, REPEAT_DELAY, nsITimer::TYPE_ONE_SHOT);
-  }
+  InitTimerCallback(REPEAT_DELAY);
   return NS_OK;
 }
 
+void
+nsRepeatService::InitTimerCallback(uint32_t aInitialDelay)
+{
+  if (mRepeatTimer) {
+    mRepeatTimer->InitWithCallback(this, aInitialDelay, nsITimer::TYPE_ONE_SHOT);
+  }
+}
+
 NS_IMPL_ISUPPORTS(nsRepeatService, nsITimerCallback)

--- a/layout/xul/nsRepeatService.h
+++ b/layout/xul/nsRepeatService.h
@@ -45,15 +45,18 @@ public:
 
   NS_DECL_ISUPPORTS
 
 protected:
   nsRepeatService();
   virtual ~nsRepeatService();
 
 private:
+  // helper function to initialize callback function to mRepeatTimer
+  void InitTimerCallback(uint32_t aInitialDelay);
+
   Callback           mCallback;
   void*              mCallbackData;
   nsCOMPtr<nsITimer> mRepeatTimer;
 
 }; // class nsRepeatService
 
 #endif