Make ensureCompositedMappingLayer() to be a void function.

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 0f135d3588e9d45dae43856a9782ce5ec12f7086..0625d9e9bdfa974026c87d275286df752e8d826b 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -2423,15 +2423,15 @@ GraphicsLayer* RenderLayer::graphicsLayerBackingForScrolling() const
     }
 }
 
-CompositedLayerMapping* RenderLayer::ensureCompositedLayerMapping()
+void RenderLayer::ensureCompositedLayerMapping()
 {
-    if (!m_compositedLayerMapping) {
-        m_compositedLayerMapping = adoptPtr(new CompositedLayerMapping(*this));
-        m_compositedLayerMapping->setNeedsGraphicsLayerUpdate(GraphicsLayerUpdateSubtree);
+    if (m_compositedLayerMapping)
+        return;
 
-        updateOrRemoveFilterEffectRenderer();
-    }
-    return m_compositedLayerMapping.get();
+    m_compositedLayerMapping = adoptPtr(new CompositedLayerMapping(*this));
+    m_compositedLayerMapping->setNeedsGraphicsLayerUpdate(GraphicsLayerUpdateSubtree);
+
+    updateOrRemoveFilterEffectRenderer();
 }
 
 void RenderLayer::clearCompositedLayerMapping(bool layerBeingDestroyed)