Revert "Remove NonCompositedContentHost" and follow-up rebaselining.

Source/core/rendering/RenderLayerCompositor.cpp

Index: Source/core/rendering/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/RenderLayerCompositor.cpp b/Source/core/rendering/RenderLayerCompositor.cpp
index 85dc6b44a54ec35b1ff3288e42453f4370ed3597..5f7b4ab1229906167ddc7693dfacb90864c32f86 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -1148,8 +1148,10 @@ void RenderLayerCompositor::frameViewDidScroll()
     // If there's a scrolling coordinator that manages scrolling for this frame view,
     // it will also manage updating the scroll layer position.
     if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator()) {
+        if (scrollingCoordinator->coordinatesScrollingForFrameView(frameView))
+            return;
         if (Settings* settings = m_renderView->document()->settings()) {
-            if (isMainFrame() || settings->compositedScrollingForFramesEnabled())
+            if (settings->compositedScrollingForFramesEnabled())
                 scrollingCoordinator->scrollableAreaScrollLayerDidChange(frameView);
         }
     }
@@ -1513,6 +1515,7 @@ bool RenderLayerCompositor::requiresOwnBackingStore(const RenderLayer* layer, co
     RenderObject* renderer = layer->renderer();
     if (compositingAncestorLayer
         && !(compositingAncestorLayer->backing()->graphicsLayer()->drawsContent()
+            || compositingAncestorLayer->backing()->paintsIntoWindow()
             || compositingAncestorLayer->backing()->paintsIntoCompositedAncestor()))
         return true;
 
@@ -2489,6 +2492,7 @@ void RenderLayerCompositor::attachRootLayer(RootLayerAttachment attachment)
     }
 
     m_rootLayerAttachment = attachment;
+    rootLayerAttachmentChanged();
 }
 
 void RenderLayerCompositor::detachRootLayer()
@@ -2523,6 +2527,7 @@ void RenderLayerCompositor::detachRootLayer()
     }
 
     m_rootLayerAttachment = RootLayerUnattached;
+    rootLayerAttachmentChanged();
 }
 
 void RenderLayerCompositor::updateRootLayerAttachment()
@@ -2535,6 +2540,15 @@ bool RenderLayerCompositor::isMainFrame() const
     return !m_renderView->document()->ownerElement();
 }
 
+void RenderLayerCompositor::rootLayerAttachmentChanged()
+{
+    // The attachment can affect whether the RenderView layer's paintsIntoWindow() behavior,
+    // so call updateGraphicsLayerGeometry() to udpate that.
+    RenderLayer* layer = m_renderView->layer();
+    if (RenderLayerBacking* backing = layer ? layer->backing() : 0)
+        backing->updateDrawsContent();
+}
+
 // IFrames are special, because we hook compositing layers together across iframe boundaries
 // when both parent and iframe content are composited. So when this frame becomes composited, we have
 // to use a synthetic style change to get the iframes into RenderLayers in order to allow them to composite.