[LayoutNG] Remove unfinished multicol+fieldset code.

Didn't intend to submit this.

TBR=cbiesinger@chromium.org

Bug: 875235
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: Iaadb3d155e24d3b15e5ccd5586c052d316131540
Reviewed-on: https://chromium-review.googlesource.com/1253981
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595426}

third_party/blink/renderer/core/layout/ng/layout_ng_fieldset.cc

@@ -56,11 +56,6 @@ void LayoutNGFieldset::AddChild(LayoutObject* new_child,
     // TODO(mstensho): Inherit all properties listed here:
     // https://html.spec.whatwg.org/multipage/rendering.html#the-fieldset-and-legend-elements
 
-    // We need to enter legacy layout from this point on, if ...
-    if (!RuntimeEnabledFeatures::LayoutNGBlockFragmentationEnabled() &&
-        new_style->SpecifiesColumns())
-      new_style->SetForceLegacyLayout(true);
-
     fieldset_content = LayoutBlock::CreateAnonymousWithParentAndDisplay(
         this, new_style->Display());
     fieldset_content->SetStyle(std::move(new_style));