Merge 146940 "Non-paintsContent fixed position layer should not ..."

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 2082 matching lines @@
             | RenderLayer::ExcludeHiddenDescendants | RenderLayer::DontConstrainForMask | RenderLayer::IncludeCompositedDescendants);
         layerBounds.scale(frameView->frame()->frameScaleFactor());
         if (!viewBounds.intersects(enclosingIntRect(layerBounds))) {
             if (viewportConstrainedNotCompositedReason)
                 *viewportConstrainedNotCompositedReason = RenderLayer::NotCompositedForBoundsOutOfView;
             return false;
         }
     }
     
     bool paintsContent = layer->isVisuallyNonEmpty() || layer->hasVisibleDescendant();
-    if (!paintsContent)
+    if (!paintsContent) {
+        if (viewportConstrainedNotCompositedReason)
+            *viewportConstrainedNotCompositedReason = RenderLayer::NotCompositedForNoVisibleContent;
         return false;
+    }
 
     return true;
 }
 
 bool RenderLayerCompositor::requiresCompositingForOverflowScrolling(const RenderLayer* layer) const
 {
     return layer->needsCompositedScrolling();
 }
 
 bool RenderLayerCompositor::isRunningAcceleratedTransformAnimation(RenderObject* renderer) const
@@ skipping 800 matching lines @@
 #if ENABLE(RUBBER_BANDING)
     info.addMember(m_layerForOverhangAreas, "layerForOverhangAreas");
     info.addMember(m_contentShadowLayer, "contentShadowLayer");
 #endif
     info.addMember(m_layerUpdater, "layerUpdater");
 }
 
 } // namespace WebCore
 
 #endif // USE(ACCELERATED_COMPOSITING)