Invalidate background obscuration after loading background images

Source/core/layout/LayoutBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 1335 matching lines @@
 {
     if (drawingBackground && (isDocumentElement() || backgroundStolenForBeingBody()))
         return false;
     for (const FillLayer* curLayer = &layers; curLayer; curLayer = curLayer->next()) {
         if (curLayer->image() && image == curLayer->image()->data()) {
             bool maybeAnimated = curLayer->image()->cachedImage() && curLayer->image()->cachedImage()->image() && curLayer->image()->cachedImage()->image()->maybeAnimated();
             if (maybeAnimated && drawingBackground)
                 setShouldDoFullPaintInvalidation(PaintInvalidationDelayedFull);
             else
                 setShouldDoFullPaintInvalidation();
+
+            if (drawingBackground)
+                invalidateBackgroundObscurationStatus();
             return true;
         }
     }
     return false;
 }
 
 bool LayoutBox::intersectsVisibleViewport()
 {
     LayoutRect rect = visualOverflowRect();
     LayoutView* layoutView = view();
@@ skipping 3370 matching lines @@
     StyleImage* borderImage = style()->borderImage().image();
     return borderImage && borderImage->canRender(*this, style()->effectiveZoom()) && borderImage->isLoaded();
 }
 
 ShapeOutsideInfo* LayoutBox::shapeOutsideInfo() const
 {
     return ShapeOutsideInfo::isEnabledFor(*this) ? ShapeOutsideInfo::info(*this) : nullptr;
 }
 
 } // namespace blink