[LayoutNG] Don't associate paint fragment to layout object for "float"

This patch chanages |NGPaintFragment::PopulateDescendants()| not to associate
paint fragments to layout object for "float" since we don't need to use them.

Change-Id: I79278a183d3bef9edac69e37de71a63aaa05ed08
Reviewed-on: https://chromium-review.googlesource.com/c/1454199Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629109}

third_party/blink/renderer/core/paint/ng/ng_paint_fragment.cc

@@ -450,7 +450,7 @@ void NGPaintFragment::PopulateDescendants(
                       std::move(previous_child), &populate_children);
 
     if (children_are_inline) {
-      if (!child_fragment->IsOutOfFlowPositioned() &&
+      if (!child_fragment->IsFloatingOrOutOfFlowPositioned() &&
           !child_fragment->IsListMarker()) {
         if (LayoutObject* layout_object = child_fragment->GetLayoutObject())
           child->AssociateWithLayoutObject(layout_object, last_fragment_map);