--- a/layout/base/nsRefreshDriver.cpp
+++ b/layout/base/nsRefreshDriver.cpp
@@ -1434,24 +1434,45 @@ nsRefreshDriver::ObserverCount() const
   sum += mPendingEvents.Length();
   sum += mFrameRequestCallbackDocs.Length();
   sum += mThrottledFrameRequestCallbackDocs.Length();
   sum += mViewManagerFlushIsPending;
   sum += mEarlyRunners.Length();
   return sum;
 }
 
-uint32_t
-nsRefreshDriver::ImageRequestCount() const
+bool
+nsRefreshDriver::HasObservers() const
 {
-  uint32_t count = 0;
+  for (uint32_t i = 0; i < ArrayLength(mObservers); ++i) {
+    if (!mObservers[i].IsEmpty()) {
+      return true;
+    }
+  }
+
+  return mViewManagerFlushIsPending ||
+         !mStyleFlushObservers.IsEmpty() ||
+         !mLayoutFlushObservers.IsEmpty() ||
+         !mResizeEventFlushObservers.IsEmpty() ||
+         !mPendingEvents.IsEmpty() ||
+         !mFrameRequestCallbackDocs.IsEmpty() ||
+         !mThrottledFrameRequestCallbackDocs.IsEmpty() ||
+         !mEarlyRunners.IsEmpty();
+}
+
+bool
+nsRefreshDriver::HasImageRequests() const
+{
   for (auto iter = mStartTable.ConstIter(); !iter.Done(); iter.Next()) {
-    count += iter.UserData()->mEntries.Count();
+    if (!iter.UserData()->mEntries.IsEmpty()) {
+      return true;
+    }
   }
-  return count + mRequests.Count();
+
+  return !mRequests.IsEmpty();
 }
 
 nsRefreshDriver::ObserverArray&
 nsRefreshDriver::ArrayFor(FlushType aFlushType)
 {
   switch (aFlushType) {
     case FlushType::Event:
       return mObservers[0];
@@ -1813,17 +1834,18 @@ nsRefreshDriver::Tick(int64_t aNowEpoch,
   if (mRootRefresh) {
     mRootRefresh->RemoveRefreshObserver(this, FlushType::Style);
     mRootRefresh = nullptr;
   }
   mSkippedPaints = false;
   mWarningThreshold = 1;
 
   nsCOMPtr<nsIPresShell> presShell = mPresContext->GetPresShell();
-  if (!presShell || (ObserverCount() == 0 && ImageRequestCount() == 0 && mScrollEvents.Length() == 0)) {
+  if (!presShell ||
+      (!HasObservers() && !HasImageRequests() && mScrollEvents.IsEmpty())) {
     // Things are being destroyed, or we no longer have any observers.
     // We don't want to stop the timer when observers are initially
     // removed, because sometimes observers can be added and removed
     // often depending on what other things are going on and in that
     // situation we don't want to thrash our timer.  So instead we
     // wait until we get a Notify() call when we have no observers
     // before stopping the timer.
     StopTimer();
@@ -2135,17 +2157,17 @@ nsRefreshDriver::Thaw()
 {
   NS_ASSERTION(mFreezeCount > 0, "Thaw() called on an unfrozen refresh driver");
 
   if (mFreezeCount > 0) {
     mFreezeCount--;
   }
 
   if (mFreezeCount == 0) {
-    if (ObserverCount() || ImageRequestCount()) {
+    if (HasObservers() || HasImageRequests()) {
       // FIXME: This isn't quite right, since our EnsureTimerStarted call
       // updates our mMostRecentRefresh, but the DoRefresh call won't run
       // and notify our observers until we get back to the event loop.
       // Thus MostRecentRefresh() will lie between now and the DoRefresh.
       RefPtr<nsRunnableMethod<nsRefreshDriver>> event = NewRunnableMethod(
         "nsRefreshDriver::DoRefresh", this, &nsRefreshDriver::DoRefresh);
       nsPresContext* pc = GetPresContext();
       if (pc) {
@@ -2160,17 +2182,17 @@ nsRefreshDriver::Thaw()
 }
 
 void
 nsRefreshDriver::FinishedWaitingForTransaction()
 {
   mWaitingForTransaction = false;
   if (mSkippedPaints &&
       !IsInRefresh() &&
-      (ObserverCount() || ImageRequestCount())) {
+      (HasObservers() || HasImageRequests())) {
     AUTO_PROFILER_TRACING("Paint", "RefreshDriverTick");
     DoRefresh();
   }
   mSkippedPaints = false;
   mWarningThreshold = 1;
 }
 
 uint64_t

--- a/layout/base/nsRefreshDriver.h
+++ b/layout/base/nsRefreshDriver.h
@@ -392,18 +392,19 @@ private:
     eNone = 0,
     eForceAdjustTimer = 1 << 0,
     eAllowTimeToGoBackwards = 1 << 1,
     eNeverAdjustTimer = 1 << 2,
   };
   void EnsureTimerStarted(EnsureTimerStartedFlags aFlags = eNone);
   void StopTimer();
 
+  bool HasObservers() const;
   uint32_t ObserverCount() const;
-  uint32_t ImageRequestCount() const;
+  bool HasImageRequests() const;
   ObserverArray& ArrayFor(mozilla::FlushType aFlushType);
   // Trigger a refresh immediately, if haven't been disconnected or frozen.
   void DoRefresh();
 
   double GetRefreshTimerInterval() const;
   double GetRegularTimerInterval(bool *outIsDefault = nullptr) const;
   static double GetThrottledTimerInterval();