Enable new multicol for testing and experimental web platform features.

Source/core/layout/LayoutObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1869 matching lines @@
         if (!child->isAnonymous() || child->style()->styleType() != NOPSEUDO)
             continue;
 
         if (blockChildrenOnly && !child->isLayoutBlock())
             continue;
 
         if (child->isLayoutFullScreen() || child->isLayoutFullScreenPlaceholder())
             continue;
 
         RefPtr<LayoutStyle> newStyle = LayoutStyle::createAnonymousStyleWithDisplay(styleRef(), child->style()->display());
-        if (!document().regionBasedColumnsEnabled()) {
+        if (!RuntimeEnabledFeatures::regionBasedColumnsEnabled()) {
             if (style()->specifiesColumns()) {
                 if (child->style()->specifiesColumns())
                     newStyle->inheritColumnPropertiesFrom(styleRef());
                 if (child->style()->columnSpan())
                     newStyle->setColumnSpan(ColumnSpanAll);
             }
         }
 
         // Preserve the position style of anonymous block continuations as they can have relative position when
         // they contain block descendants of relative positioned inlines.
@@ skipping 1325 matching lines @@
 {
     if (object1) {
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     }
 }
 
 #endif