Update setting of Compositor on new root Layer

ui/compositor/layer_owner.cc

Index: ui/compositor/layer_owner.cc
diff --git a/ui/compositor/layer_owner.cc b/ui/compositor/layer_owner.cc
index 227dfa9b364b6c514d0c9affdab6a53968fcbc6e..d874b4769f184d196edd39512ebfd65eb9f18ed1 100644
--- a/ui/compositor/layer_owner.cc
+++ b/ui/compositor/layer_owner.cc
@@ -52,10 +52,14 @@ scoped_ptr<Layer> LayerOwner::RecreateLayer() {
   if (alpha_shape)
     new_layer->SetAlphaShape(make_scoped_ptr(new SkRegion(*alpha_shape)));
 
-  // Install new layer as a sibling of the old layer, stacked below it.
   if (old_layer->parent()) {
+    // Install new layer as a sibling of the old layer, stacked below it.
     old_layer->parent()->Add(new_layer);
     old_layer->parent()->StackBelow(new_layer, old_layer.get());
+  } else if (old_layer->GetCompositor()) {
+    // If old_layer was the layer tree root then we need to move the Compositor
+    // over to the new root.
+    old_layer->GetCompositor()->SetRootLayer(new_layer);
   }
 
   // Migrate all the child layers over to the new layer. Copy the list because
@@ -68,12 +72,6 @@ scoped_ptr<Layer> LayerOwner::RecreateLayer() {
     new_layer->Add(child);
   }
 
-  // If old_layer was the layer tree root then we need to move the Compositor
-  // over to the new root.
-  const bool is_root = !old_layer->parent();
-  if (is_root && old_layer->GetCompositor())
-    old_layer->GetCompositor()->SetRootLayer(new_layer);
-
   // Install the delegate last so that the delegate isn't notified as we copy
   // state to the new layer.
   new_layer->set_delegate(old_delegate);