Generalize visible descendant dirty bits to prepare for more properties.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 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 1754 matching lines @@
           m_layerForHorizontalScrollbar, false,
           CompositingReasonLayerForHorizontalScrollbar);
     if (m_layerForVerticalScrollbar && needsVerticalScrollbarLayer &&
         scrollableArea->shouldRebuildVerticalScrollbarLayer())
       toggleScrollbarLayerIfNeeded(m_layerForVerticalScrollbar, false,
                                    CompositingReasonLayerForVerticalScrollbar);
     scrollableArea->resetRebuildScrollbarLayerFlags();
   }
 
   // If the subtree is invisible, we don't actually need scrollbar layers.
-  bool invisible = m_owningLayer.subtreeIsInvisible();
-  needsHorizontalScrollbarLayer &= !invisible;
-  needsVerticalScrollbarLayer &= !invisible;
-  needsScrollCornerLayer &= !invisible;
+  // Only do this check if at least one of the bits is currently true.
+  // This is important because this method is called during the destructor
+  // of CompositedLayerMapping, which may happen during style recalc,
+  // and therefore visible content status may be invalid.
+  if (needsHorizontalScrollbarLayer || needsVerticalScrollbarLayer ||
+      needsScrollCornerLayer) {
+    bool invisible = m_owningLayer.subtreeIsInvisible();
+    needsHorizontalScrollbarLayer &= !invisible;
+    needsVerticalScrollbarLayer &= !invisible;
+    needsScrollCornerLayer &= !invisible;
+  }
 
   bool horizontalScrollbarLayerChanged = toggleScrollbarLayerIfNeeded(
       m_layerForHorizontalScrollbar, needsHorizontalScrollbarLayer,
       CompositingReasonLayerForHorizontalScrollbar);
   bool verticalScrollbarLayerChanged = toggleScrollbarLayerIfNeeded(
       m_layerForVerticalScrollbar, needsVerticalScrollbarLayer,
       CompositingReasonLayerForVerticalScrollbar);
   bool scrollCornerLayerChanged = toggleScrollbarLayerIfNeeded(
       m_layerForScrollCorner, needsScrollCornerLayer,
       CompositingReasonLayerForScrollCorner);
@@ skipping 1569 matching lines @@
   } else if (graphicsLayer == m_decorationOutlineLayer.get()) {
     name = "Decoration Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink