--- a/layout/xul/nsRepeatService.cpp
+++ b/layout/xul/nsRepeatService.cpp
@@ -6,21 +6,22 @@
 //
 // Eric Vaughan
 // Netscape Communications
 //
 // See documentation in associated header file
 //
 
 #include "nsRepeatService.h"
+#include "mozilla/StaticPtr.h"
 #include "nsIServiceManager.h"
 
 using namespace mozilla;
 
-static StaticRefPtr<nsRepeatService> gRepeatService;
+static StaticAutoPtr<nsRepeatService> gRepeatService;
 
 nsRepeatService::nsRepeatService()
 : mCallback(nullptr), mCallbackData(nullptr)
 {
 }
 
 nsRepeatService::~nsRepeatService()
 {
@@ -66,28 +67,32 @@ void nsRepeatService::Stop(Callback aCal
   if (mRepeatTimer) {
      mRepeatTimer->Cancel();
      mRepeatTimer = nullptr;
   }
   mCallback = nullptr;
   mCallbackData = nullptr;
 }
 
-NS_IMETHODIMP nsRepeatService::Notify(nsITimer *timer)
-{
-  // do callback
-  if (mCallback)
-    mCallback(mCallbackData);
-
-  // start timer again.
-  InitTimerCallback(REPEAT_DELAY);
-  return NS_OK;
-}
-
 void
 nsRepeatService::InitTimerCallback(uint32_t aInitialDelay)
 {
-  if (mRepeatTimer) {
-    mRepeatTimer->InitWithCallback(this, aInitialDelay, nsITimer::TYPE_ONE_SHOT);
+  if (!mRepeatTimer) {
+    return;
   }
-}
 
-NS_IMPL_ISUPPORTS(nsRepeatService, nsITimerCallback)
+  mRepeatTimer->InitWithFuncCallback([](nsITimer* aTimer, void* aClosure) {
+    // Use gRepeatService instead of nsRepeatService::GetInstance() (because
+    // we don't want nsRepeatService::GetInstance() to re-create a new instance
+    // for us, if we happen to get invoked after nsRepeatService::Shutdown() has
+    // nulled out gRepeatService).
+    nsRepeatService* rs = gRepeatService;
+    if (!rs) {
+      return;
+    }
+
+    if (rs->mCallback) {
+      rs->mCallback(rs->mCallbackData);
+    }
+
+    rs->InitTimerCallback(REPEAT_DELAY);
+  }, nullptr, aInitialDelay, nsITimer::TYPE_ONE_SHOT);
+}

--- a/layout/xul/nsRepeatService.h
+++ b/layout/xul/nsRepeatService.h
@@ -17,42 +17,38 @@
 #ifdef XP_MACOSX
 #define REPEAT_DELAY        25
 #else
 #define REPEAT_DELAY        50
 #endif
 
 class nsITimer;
 
-class nsRepeatService final : public nsITimerCallback
+class nsRepeatService final
 {
 public:
+  typedef void (* Callback)(void* aData);
 
-  typedef void (* Callback)(void* aData);
-    
-  NS_DECL_NSITIMERCALLBACK
+  ~nsRepeatService();
 
   // Start dispatching timer events to the callback. There is no memory
   // management of aData here; it is the caller's responsibility to call
   // Stop() before aData's memory is released.
   void Start(Callback aCallback, void* aData,
              uint32_t aInitialDelay = INITAL_REPEAT_DELAY);
   // Stop dispatching timer events to the callback. If the repeat service
   // is not currently configured with the given callback and data, this
   // is just ignored.
   void Stop(Callback aCallback, void* aData);
 
   static nsRepeatService* GetInstance();
   static void Shutdown();
 
-  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;