Only boxes should have child transform layers.

Source/core/rendering/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 458 matching lines @@
 
     if (updateOverflowControlsLayers(requiresHorizontalScrollbarLayer(), requiresVerticalScrollbarLayer(), requiresScrollCornerLayer()))
         layerConfigChanged = true;
 
     if (updateScrollingLayers(m_owningLayer.needsCompositedScrolling()))
         layerConfigChanged = true;
 
     bool hasPerspective = false;
     if (RenderStyle* style = renderer->style())
         hasPerspective = style->hasPerspective();
-    bool needsChildTransformLayer = hasPerspective && (layerForChildrenTransform() == m_childTransformLayer.get());
+    bool needsChildTransformLayer = hasPerspective && (layerForChildrenTransform() == m_childTransformLayer.get()) && renderer->isBox();

[Julien - ping for review, 2014/04/17 00:02:38]

Wouldn't it make more sense not to have a RenderLayer in the non-box case as we
won't apply the perspective anyway?

[Ian Vollick, 2014/04/17 01:31:03]

I don't think that's possible here. You couldn't be composited without a
RenderLayer, but we do need a composited layer to pass on opacity info to the
composited descedants.

     if (updateChildTransformLayer(needsChildTransformLayer))
         layerConfigChanged = true;
 
     updateScrollParent(scrollParent);
     updateClipParent(m_owningLayer.clipParent());
 
     if (updateSquashingLayers(!m_squashedLayers.isEmpty()))
         layerConfigChanged = true;
 
     if (layerConfigChanged)
@@ skipping 1667 matching lines @@
     } else if (graphicsLayer == m_scrollingContentsLayer.get()) {
         name = "Scrolling Contents Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore