[LayoutNG] Switch NGBreakToken to being RefCounted.

third_party/WebKit/Source/core/layout/ng/ng_physical_box_fragment.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/ng/ng_physical_box_fragment.h"
 
 #include "core/layout/ng/ng_floating_object.h"
 
 namespace blink {
 
 NGPhysicalBoxFragment::NGPhysicalBoxFragment(
     LayoutObject* layout_object,
     NGPhysicalSize size,
     NGPhysicalSize overflow,
     Vector<RefPtr<NGPhysicalFragment>>& children,
     Vector<Persistent<NGFloatingObject>>& positioned_floats,
     const WTF::Optional<NGLogicalOffset>& bfc_offset,
     const NGMarginStrut& end_margin_strut,
-    NGBreakToken* break_token)
+    RefPtr<NGBreakToken> break_token)
     : NGPhysicalFragment(layout_object,
                          size,
                          overflow,
                          kFragmentBox,
-                         break_token),
+                         std::move(break_token)),
       positioned_floats_(positioned_floats),
       bfc_offset_(bfc_offset),
       end_margin_strut_(end_margin_strut) {
   children_.swap(children);
 }
 
 }  // namespace blink