--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -440,19 +440,16 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(
 NS_INTERFACE_MAP_END
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(nsPresContext)
 NS_IMPL_CYCLE_COLLECTING_RELEASE_WITH_LAST_RELEASE(nsPresContext, LastRelease())
 
 void
 nsPresContext::LastRelease()
 {
-  if (IsRoot()) {
-    static_cast<nsRootPresContext*>(this)->CancelAllDidPaintTimers();
-  }
   if (mMissingFonts) {
     mMissingFonts->Clear();
   }
 }
 
 NS_IMPL_CYCLE_COLLECTION_CLASS(nsPresContext)
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsPresContext)
@@ -1109,19 +1106,16 @@ nsPresContext::DetachShell()
   }
 
   if (IsRoot()) {
     nsRootPresContext* thisRoot = static_cast<nsRootPresContext*>(this);
 
     // Have to cancel our plugin geometry timer, because the
     // callback for that depends on a non-null presshell.
     thisRoot->CancelApplyPluginGeometryTimer();
-
-    // The did-paint timer also depends on a non-null pres shell.
-    thisRoot->CancelAllDidPaintTimers();
   }
 }
 
 void
 nsPresContext::DoChangeCharSet(NotNull<const Encoding*> aCharSet)
 {
   UpdateCharSet(aCharSet);
   mDeviceContext->FlushFontCache();
@@ -2613,34 +2607,22 @@ nsPresContext::NotifyInvalidation(uint64
   NotifyInvalidation(aTransactionId, rect);
 }
 
 void
 nsPresContext::NotifyInvalidation(uint64_t aTransactionId, const nsRect& aRect)
 {
   MOZ_ASSERT(GetContainerWeak(), "Invalidation in detached pres context");
 
-  // If there is no paint event listener, then we don't need to fire
-  // the asynchronous event. We don't even need to record invalidation.
-  // MayHavePaintEventListener is pretty cheap and we could make it
-  // even cheaper by providing a more efficient
-  // nsPIDOMWindow::GetListenerManager.
-
   nsPresContext* pc;
   for (pc = this; pc; pc = pc->GetParentPresContext()) {
     if (pc->mFireAfterPaintEvents)
       break;
     pc->mFireAfterPaintEvents = true;
   }
-  if (!pc) {
-    nsRootPresContext* rpc = GetRootPresContext();
-    if (rpc) {
-      rpc->EnsureEventualDidPaintEvent(aTransactionId);
-    }
-  }
 
   TransactionInvalidations* transaction = nullptr;
   for (TransactionInvalidations& t : mTransactions) {
     if (t.mTransactionId == aTransactionId) {
       transaction = &t;
       break;
     }
   }
@@ -2752,22 +2734,18 @@ public:
   const mozilla::TimeStamp mTimeStamp;
   nsTArray<nsRect> mList;
 };
 
 void
 nsPresContext::NotifyDidPaintForSubtree(uint64_t aTransactionId,
                                         const mozilla::TimeStamp& aTimeStamp)
 {
-  if (IsRoot()) {
-    static_cast<nsRootPresContext*>(this)->CancelDidPaintTimers(aTransactionId);
-
-    if (!mFireAfterPaintEvents) {
-      return;
-    }
+  if (IsRoot() && !mFireAfterPaintEvents) {
+    return;
   }
 
   if (!PresShell()->IsVisible() && !mFireAfterPaintEvents) {
     return;
   }
 
   // Non-root prescontexts fire MozAfterPaint to all their descendants
   // unconditionally, even if no invalidations have been collected. This is
@@ -3186,24 +3164,22 @@ nsRootPresContext::nsRootPresContext(nsI
   : nsPresContext(aDocument, aType)
 {
 }
 
 nsRootPresContext::~nsRootPresContext()
 {
   NS_ASSERTION(mRegisteredPlugins.Count() == 0,
                "All plugins should have been unregistered");
-  CancelAllDidPaintTimers();
   CancelApplyPluginGeometryTimer();
 }
 
 /* virtual */ void
 nsRootPresContext::Detach()
 {
-  CancelAllDidPaintTimers();
   // XXXmats maybe also CancelApplyPluginGeometryTimer(); ?
   nsPresContext::Detach();
 }
 
 void
 nsRootPresContext::RegisterPluginForGeometryUpdates(nsIContent* aPlugin)
 {
   mRegisteredPlugins.PutEntry(aPlugin);
@@ -3449,65 +3425,16 @@ nsRootPresContext::CollectPluginGeometry
   if (clm) {
     clm->StorePluginWidgetConfigurations(configurations);
   }
   PluginDidSetGeometry(mRegisteredPlugins);
 #endif  // #ifndef XP_MACOSX
 }
 
 void
-nsRootPresContext::EnsureEventualDidPaintEvent(uint64_t aTransactionId)
-{
-  for (NotifyDidPaintTimer& t : mNotifyDidPaintTimers) {
-    if (t.mTransactionId == aTransactionId) {
-      return;
-    }
-  }
-
-  nsCOMPtr<nsITimer> timer;
-  RefPtr<nsRootPresContext> self = this;
-  nsresult rv = NS_NewTimerWithCallback(
-    getter_AddRefs(timer),
-    NewNamedTimerCallback([self, aTransactionId](){
-      nsAutoScriptBlocker blockScripts;
-      self->NotifyDidPaintForSubtree(aTransactionId);
-     }, "NotifyDidPaintForSubtree"), 100, nsITimer::TYPE_ONE_SHOT,
-    Document()->EventTargetFor(TaskCategory::Other));
-
-  if (NS_SUCCEEDED(rv)) {
-    NotifyDidPaintTimer* t = mNotifyDidPaintTimers.AppendElement();
-    t->mTransactionId = aTransactionId;
-    t->mTimer = timer;
-  }
-}
-
-void
-nsRootPresContext::CancelDidPaintTimers(uint64_t aTransactionId)
-{
-  uint32_t i = 0;
-  while (i < mNotifyDidPaintTimers.Length()) {
-    if (mNotifyDidPaintTimers[i].mTransactionId <= aTransactionId) {
-      mNotifyDidPaintTimers[i].mTimer->Cancel();
-      mNotifyDidPaintTimers.RemoveElementAt(i);
-    } else {
-      i++;
-    }
-  }
-}
-
-void
-nsRootPresContext::CancelAllDidPaintTimers()
-{
-  for (uint32_t i = 0; i < mNotifyDidPaintTimers.Length(); i++) {
-    mNotifyDidPaintTimers[i].mTimer->Cancel();
-  }
-  mNotifyDidPaintTimers.Clear();
-}
-
-void
 nsRootPresContext::AddWillPaintObserver(nsIRunnable* aRunnable)
 {
   if (!mWillPaintFallbackEvent.IsPending()) {
     mWillPaintFallbackEvent = new RunWillPaintObservers(this);
     Document()->Dispatch(TaskCategory::Other,
                          do_AddRef(mWillPaintFallbackEvent));
   }
   mWillPaintObservers.AppendElement(aRunnable);
@@ -3529,13 +3456,12 @@ nsRootPresContext::FlushWillPaintObserve
 
 size_t
 nsRootPresContext::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
 {
   return nsPresContext::SizeOfExcludingThis(aMallocSizeOf);
 
   // Measurement of the following members may be added later if DMD finds it is
   // worthwhile:
-  // - mNotifyDidPaintTimer
   // - mRegisteredPlugins
   // - mWillPaintObservers
   // - mWillPaintFallbackEvent
 }

--- a/layout/base/nsPresContext.h
+++ b/layout/base/nsPresContext.h
@@ -1536,33 +1536,16 @@ public:
 
 class nsRootPresContext final : public nsPresContext {
 public:
   nsRootPresContext(nsIDocument* aDocument, nsPresContextType aType);
   virtual ~nsRootPresContext();
   virtual void Detach() override;
 
   /**
-   * Ensure that NotifyDidPaintForSubtree is eventually called on this
-   * object after a timeout.
-   */
-  void EnsureEventualDidPaintEvent(uint64_t aTransactionId);
-
-  /**
-   * Cancels any pending eventual did paint timer for transaction
-   * ids up to and including aTransactionId.
-   */
-  void CancelDidPaintTimers(uint64_t aTransactionId);
-
-  /**
-   * Cancel all pending eventual did paint timers.
-   */
-  void CancelAllDidPaintTimers();
-
-  /**
    * Registers a plugin to receive geometry updates (position and clip
    * region) so it can update its widget.
    * Callers must call UnregisterPluginForGeometryUpdates before
    * the aPlugin frame is destroyed.
    */
   void RegisterPluginForGeometryUpdates(nsIContent* aPlugin);
   /**
    * Stops a plugin receiving geometry updates (position and clip
@@ -1643,22 +1626,16 @@ protected:
       return NS_OK;
     }
     // The lifetime of this reference is handled by an nsRevocableEventPtr
     nsRootPresContext* MOZ_NON_OWNING_REF mPresContext;
   };
 
   friend class nsPresContext;
 
-  struct NotifyDidPaintTimer {
-    uint64_t mTransactionId;
-    nsCOMPtr<nsITimer> mTimer;
-  };
-  AutoTArray<NotifyDidPaintTimer, 4> mNotifyDidPaintTimers;
-
   nsCOMPtr<nsITimer> mApplyPluginGeometryTimer;
   nsTHashtable<nsRefPtrHashKey<nsIContent> > mRegisteredPlugins;
   nsTArray<nsCOMPtr<nsIRunnable> > mWillPaintObservers;
   nsRevocableEventPtr<RunWillPaintObservers> mWillPaintFallbackEvent;
 };
 
 #ifdef MOZ_REFLOW_PERF