Revert "Remove empty layer hack in RenderLayerCompositor"

Source/WebCore/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 633 matching lines @@
 
 void RenderLayerCompositor::addToOverlapMap(OverlapMap& overlapMap, RenderLayer* layer, IntRect& layerBounds, bool& boundsComputed)
 {
     if (layer->isRootLayer())
         return;
 
     if (!boundsComputed) {
         // FIXME: If this layer's overlap bounds include its children, we don't need to add its
         // children's bounds to the overlap map.
         layerBounds = enclosingIntRect(overlapMap.geometryMap().absoluteRect(layer->overlapBounds()));
+        // Empty rects never intersect, but we need them to for the purposes of overlap testing.
+        if (layerBounds.isEmpty())
+            layerBounds.setSize(IntSize(1, 1));
         boundsComputed = true;
-        if (layerBounds.isEmpty())
-            return;
     }
 
     IntRect clipRect = pixelSnappedIntRect(layer->backgroundClipRect(RenderLayer::ClipRectsContext(rootRenderLayer(), 0, AbsoluteClipRects)).rect()); // FIXME: Incorrect for CSS regions.
     clipRect.intersect(layerBounds);
     overlapMap.add(layer, clipRect);
 }
 
 void RenderLayerCompositor::addToOverlapMapRecursive(OverlapMap& overlapMap, RenderLayer* layer, RenderLayer* ancestorLayer)
 {
     if (!canBeComposited(layer) || overlapMap.contains(layer))
@@ skipping 63 matching lines @@
     layer->setHasCompositingDescendant(false);
     
     RenderLayer::IndirectCompositingReason compositingReason = compositingState.m_subtreeIsCompositing ? RenderLayer::IndirectCompositingForStacking : RenderLayer::NoIndirectCompositingReason;
 
     bool haveComputedBounds = false;
     IntRect absBounds;
     if (overlapMap && !overlapMap->isEmpty() && compositingState.m_testingOverlap) {
         // If we're testing for overlap, we only need to composite if we overlap something that is already composited.
         absBounds = enclosingIntRect(overlapMap->geometryMap().absoluteRect(layer->overlapBounds()));
 
+        // Empty rects never intersect, but we need them to for the purposes of overlap testing.
+        if (absBounds.isEmpty())
+            absBounds.setSize(IntSize(1, 1));
         haveComputedBounds = true;
         compositingReason = overlapMap->overlapsLayers(absBounds) ? RenderLayer::IndirectCompositingForOverlap : RenderLayer::NoIndirectCompositingReason;
     }
 
 #if ENABLE(VIDEO)
     // Video is special. It's the only RenderLayer type that can both have
     // RenderLayer children and whose children can't use its backing to render
     // into. These children (the controls) always need to be promoted into their
     // own layers to draw on top of the accelerated video.
     if (compositingState.m_compositingAncestor && compositingState.m_compositingAncestor->renderer()->isVideo())
@@ skipping 2028 matching lines @@
     info.addMember(m_layerForOverhangAreas, "layerForOverhangAreas");
     info.addMember(m_contentShadowLayer, "contentShadowLayer");
     info.addMember(m_layerForTopOverhangArea, "layerForTopOverhangArea");
     info.addMember(m_layerForBottomOverhangArea, "layerForBottomOverhangArea");
     info.addMember(m_layerForHeader, "layerForHeader");
     info.addMember(m_layerForFooter, "layerForFooter");
 #endif
 }
 
 } // namespace WebCore