--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -270,18 +270,23 @@ nsDOMWindowUtils::Redraw(uint32_t aCount
   }
   return NS_ERROR_FAILURE;
 }
 
 NS_IMETHODIMP
 nsDOMWindowUtils::UpdateLayerTree()
 {
   if (nsIPresShell* presShell = GetPresShell()) {
+    presShell->FlushPendingNotifications(Flush_Display);
     nsRefPtr<nsViewManager> vm = presShell->GetViewManager();
-    vm->ProcessPendingUpdates();
+    nsView* view = vm->GetRootView();
+    if (view) {
+      presShell->Paint(view, view->GetBounds(),
+          nsIPresShell::PAINT_LAYERS | nsIPresShell::PAINT_SYNC_DECODE_IMAGES);
+    }
   }
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsDOMWindowUtils::SetCSSViewport(float aWidthPx, float aHeightPx)
 {
   if (!nsContentUtils::IsCallerChrome()) {

--- a/layout/base/nsIPresShell.h
+++ b/layout/base/nsIPresShell.h
@@ -1419,16 +1419,18 @@ public:
 
   enum PaintFlags {
     /* Update the layer tree and paint PaintedLayers. If this is not specified,
      * we may still have to do it if the layer tree lost PaintedLayer contents
      * we need for compositing. */
     PAINT_LAYERS = 0x01,
     /* Composite layers to the window. */
     PAINT_COMPOSITE = 0x02,
+    /* Sync-decode images. */
+    PAINT_SYNC_DECODE_IMAGES = 0x04
   };
   virtual void Paint(nsView* aViewToPaint, const nsRegion& aDirtyRegion,
                      uint32_t aFlags) = 0;
   virtual nsresult HandleEvent(nsIFrame* aFrame,
                                mozilla::WidgetGUIEvent* aEvent,
                                bool aDontRetargetEvents,
                                nsEventStatus* aEventStatus) = 0;
   virtual bool ShouldIgnoreInvalidation() = 0;

--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -6265,17 +6265,18 @@ PresShell::Paint(nsView*        aViewToP
 
     if (!(aFlags & PAINT_LAYERS)) {
       if (layerManager->EndEmptyTransaction()) {
         return;
       }
       NS_WARNING("Must complete empty transaction when compositing!");
     }
 
-    if (!(frame->GetStateBits() & NS_FRAME_UPDATE_LAYER_TREE) &&
+    if (!(aFlags & PAINT_SYNC_DECODE_IMAGES) &&
+        !(frame->GetStateBits() & NS_FRAME_UPDATE_LAYER_TREE) &&
         !mNextPaintCompressed) {
       NotifySubDocInvalidationFunc computeInvalidFunc =
         presContext->MayHavePaintEventListenerInSubDocument() ? nsPresContext::NotifySubDocInvalidation : 0;
       bool computeInvalidRect = computeInvalidFunc ||
                                 (layerManager->GetBackendType() == LayersBackend::LAYERS_BASIC);
 
       UniquePtr<LayerProperties> props;
       if (computeInvalidRect) {
@@ -6318,16 +6319,19 @@ PresShell::Paint(nsView*        aViewToP
     frame->ClearPresShellsFromLastPaint();
   }
 
   nscolor bgcolor = ComputeBackstopColor(aViewToPaint);
   uint32_t flags = nsLayoutUtils::PAINT_WIDGET_LAYERS | nsLayoutUtils::PAINT_EXISTING_TRANSACTION;
   if (!(aFlags & PAINT_COMPOSITE)) {
     flags |= nsLayoutUtils::PAINT_NO_COMPOSITE;
   }
+  if (aFlags & PAINT_SYNC_DECODE_IMAGES) {
+    flags |= nsLayoutUtils::PAINT_SYNC_DECODE_IMAGES;
+  }
   if (mNextPaintCompressed) {
     flags |= nsLayoutUtils::PAINT_COMPRESSED;
     mNextPaintCompressed = false;
   }
 
   if (frame) {
     // We can paint directly into the widget using its layer manager.
     nsLayoutUtils::PaintFrame(nullptr, frame, aDirtyRegion, bgcolor, flags);