Refactor the API for setting dynamic resource load priorities

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 1324 matching lines @@
         if (!info.isComputingShape()) {
             info.markShapeAsDirty();
             markShapeOutsideDependentsForLayout();
         }
     }
 
     if (!invalidatePaintOfLayerRectsForImage(image, style()->backgroundLayers(), true))
         invalidatePaintOfLayerRectsForImage(image, style()->maskLayers(), false);
 }
 
+ResourcePriority LayoutBox::updatePriority(Resource*)
+{
+    LayoutRect viewBounds = viewRect();
+    LayoutRect objectBounds = LayoutRect(absoluteContentBox());
+
+    // The object bounds might be empty right now, so intersects will fail since it doesn't deal
+    // with empty rects. Use LayoutRect::contains in that case.
+    bool isVisible;
+    if (!objectBounds.isEmpty())
+        isVisible =  viewBounds.intersects(objectBounds);
+    else
+        isVisible = viewBounds.contains(objectBounds);
+
+    LayoutRect screenRect;
+    if (!objectBounds.isEmpty()) {
+        screenRect = viewBounds;
+        screenRect.intersect(objectBounds);
+    }
+
+    int screenArea = 0;
+    if (!screenRect.isEmpty() && isVisible)
+        screenArea = static_cast<uint32_t>(screenRect.width() * screenRect.height());
+    return ResourcePriority(isVisible ? ResourcePriority::Visible : ResourcePriority::NotVisible, screenArea);
+}
+
 bool LayoutBox::invalidatePaintOfLayerRectsForImage(WrappedImagePtr image, const FillLayer& layers, bool drawingBackground)
 {
     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
@@ skipping 3384 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