AttachLayoutTree on a new Document not necessary.

We called AttachLayoutTree on a new Document which just got its
LayoutView created. It will not do anything useful as the document does
not yet have any child nodes.

Change-Id: I1af44b96b86dcb0a597c662b4c47fe9ab3d972aa
Reviewed-on: https://chromium-review.googlesource.com/c/1317889Reviewed-by: Anders Ruud <andruud@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605372}

third_party/blink/renderer/core/dom/document.cc

@@ -2744,13 +2744,6 @@ void Document::Initialize() {
   layout_view_->Compositor()->SetNeedsCompositingUpdate(
       kCompositingUpdateAfterCompositingInputChange);
 
-  {
-    ReattachLegacyLayoutObjectList legacy_layout_objects(*this);
-    AttachContext context;
-    ContainerNode::AttachLayoutTree(context);
-    legacy_layout_objects.ForceLegacyLayoutIfNeeded();
-  }
-
   // The TextAutosizer can't update layout view info while the Document is
   // detached, so update now in case anything changed.
   if (TextAutosizer* autosizer = GetTextAutosizer())