Fix chicken and egg problem in composited bounds computation

Source/core/rendering/RenderLayer.cpp

Index: Source/core/rendering/RenderLayer.cpp
diff --git a/Source/core/rendering/RenderLayer.cpp b/Source/core/rendering/RenderLayer.cpp
index f78fdbb8cd0b745c480cd3b63aefe0415c32752b..138492f7ba689979912345c5a6ca2640ba8c27ca 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -3600,6 +3600,14 @@ IntRect RenderLayer::calculateLayerBounds(const RenderLayer* ancestorLayer, cons
     // This applies to all z-order lists below.
     RenderLayerStackingNodeIterator iterator(*m_stackingNode.get(), AllChildren);
     while (RenderLayerStackingNode* node = iterator.next()) {
+        // Node's compositing ancestor may have changed its draw content status
+        // prior to updating its bounds. The requires-own-backing-store-for-ancestor-reasons
+        // could be stale. Refresh them now.
+        if (node->layer()->hasCompositedLayerMapping()) {
+            RenderLayer* enclosingCompositingLayer = node->layer()->enclosingCompositingLayer(false);
+            node->layer()->compositedLayerMapping()->updateRequiresOwnBackingStoreForAncestorReasons(enclosingCompositingLayer);
+        }
+
         if (flags & IncludeCompositedDescendants || !node->layer()->hasCompositedLayerMapping()) {
             IntRect childUnionBounds = node->layer()->calculateLayerBounds(this, 0, descendantFlags);
             unionBounds.unite(childUnionBounds);