Revert "Remove NonCompositedContentHost" and follow-up rebaselining.

Source/core/rendering/RenderLayerBacking.h

Index: Source/core/rendering/RenderLayerBacking.h
diff --git a/Source/core/rendering/RenderLayerBacking.h b/Source/core/rendering/RenderLayerBacking.h
index 86ef06a36c74389aa28778b6d780ec4cf735d288..29127e0125eb527a825f733f302cea116d077c0f 100644
--- a/Source/core/rendering/RenderLayerBacking.h
+++ b/Source/core/rendering/RenderLayerBacking.h
@@ -100,6 +100,14 @@ public:
     GraphicsLayer* parentForSublayers() const;
     GraphicsLayer* childForSuperlayers() const;
 
+    // RenderLayers with backing normally short-circuit paintLayer() because
+    // their content is rendered via callbacks from GraphicsLayer. However, the document
+    // layer is special, because it has a GraphicsLayer to act as a container for the GraphicsLayers
+    // for descendants, but its contents usually render into the window (in which case this returns true).
+    // This returns false for other layers, and when the document layer actually needs to paint into its backing store
+    // for some reason.
+    bool paintsIntoWindow() const;
+    
     // Returns true for a composited layer that has no backing store of its own, so
     // paints into some ancestor layer.
     bool paintsIntoCompositedAncestor() const { return !m_requiresOwnBackingStore; }